Emma Carstairs is excited about going to train with her best friend, Julian (Jules) while her parents are out on assignment. She practices with the sword her dad gave her. The doorbell rings and then they hear screaming. The tutorer, Katerina, and Jule’s half brother, Mark, go to see what is happening. Jules takes the twins to the office and sends Emma to get Drusilla (8) and Tavvy (2) and meet them. She gets them and starts leading them to the office when she sees Sebastian make Katerina drink from the Infernal Cup. Sebastian realizes that Mark is half fairy and doesn’t want him. Emma throws a star at him and the new Shadowhunters, now called Endarkened. She runs to the office where Jules is begging the Clave to keep the portal open a little longer. They leave it open just long enough for Jules and Emma to get through.
Jace is outside sitting in the grass with Jordan, learning how to meditate to control the heavenly fire that runs through his veins. Clary and Simon arrive and Jordan leaves them to go meet Maia. Jace and Clary join their friends and find Alec moping about Magnus. Jace breaks his phone so that he will stop calling his exboyfriend. Isabelle gets a text from Maryse instructing them to return for another meeting. The Clave has been interviewing them all about what happened at the Burren, trying to figure out Sebastian’s next move. The Silent Brothers have tried to harness the heavenly fire in Jace with no luck. Clary goes Christmas shopping with Simon. Jace goes to talk to Magnus about Alec. Clary decides to get Jace sheet music (suggested by Simon). She then takes Simon into Sephora to find something for Isabelle. They talk about how much things have changed and Clary suggests that Simon talk to Raphael about how to live as a vampire. Jocelyn comes in, relieved that Clary is alright, and says they have to go to the Institute right away. Jace tries to talk to Magnus, trying to get him to forgive Alec. Magnus deflects questions about himself and Jace points it out. Isabelle calls and tells Jace to come home immediately. Magnus asks if Alec is okay, but Jace refuses to answer. In the Institute library, everyone is reunited. Maryse explains that Sebastian has been attacking Institutes to gather soldiers. The Clave is calling for evacuation of all Institutes to Idris, where the wards will be doubled, no one in, no one out.
Emma wakes up. Helen (Aline’s girlfriend) tells her what happened. Emma asks about her parents and Helen explains that they found their bodies that morning. Emma screams until Julian brings her Cortana, the Carstairs sword. She knows she has to be strong. Shadowhunters gather from all over New York to go through a portal to Idris. Simon is on the Institute grounds to say goodbye to Clary. They talk about his relationship with Isabelle, who approaches him after Clary says everything she needs to. Magnus shows up to see Alec. They both realize that they are to blame for the end of their relationship and that i can’t go on. Magnus tells him that he needs him to live through what is coming. Simon and Isabelle share a moment. She gives him her ruby necklace (detects demons) as a loan until they see each other again. She tells him not to date anyone else while she is gone and joins Alec in going through the portal. Simon watches everyone go through, including Clary, who goes last.
Clary, Jocelyn, and Luke stay at Amatis’ house in Alicante. Clary tires to get some sleep, but is unable. She goes downstairs and ends up eavesdropping on her mom and Luke’s conversation. Somehow, the box of her brother’s baby things made it into the house from Valentine’s apartment. They will have to tell the Clave. The Shadowhunters all cram into a hall for the Council meeting. Jia Penhallow (Aline’s mother) leads the discussion as the new Consul. The Blackthorn children are trotted out onto stage. the new Inquisitor, Robert Lightwood, gives Julian the mortal sword and starts asking him questions. Emma runs up to defend Julian, as she can tell that the Moral Sword causes pain. She grabs it, tells her story, and runs away. Clary gets up and runs after her. She finds Emma and talks with her for a while, helping to calm her down. Jace comes to get Clary and Emma realizes who they both are. Clary tells Emma she can come to talk to them anytime.
Clary goes to the house reserved for the Inquisitor. Robert answers the door and sends her to the top floor where his children are. When Clary joins them, they are speculating what Sebastian’s next move will be. They fill Clary in on what she missed during the meeting (talking about Jace being their only source of heavenly fire and how to cure the Endarkened). Isabelle thinks they should focus on killing Sebastian. Alec upsets her with a comment about their parents splitting up because of Max’s death. He goes after her and Jace wants to walk Clary home. simon, Maia, and Jordan are sitting around talking about Simon’s life and relationship with Isabelle. There is a knock on the door and the Daylighter goes to answer it, expecting it to be their take-out food. There is an Endarkened at the door. Jordan and Maia start fighting him off and send Simon away. He makes it down the fire escape before he is confronted by Lily and Zeke, two of Maureen’s vampires. Jace starts to walk Clary home. She tells him that Emma reminds her of him and knows the little girl will have to learn the same things Jace did growing up. He pulls her into an alley and they start kissing. he pulls away and shows her that his hands left scorch marks on the wall. Sebastian and the Seelie Queen lie in bed together. Meliorn (who has a seat on the Council) tells them that everyone is being evacuated to Idris, but a few Institutes still have Shadowhunters left. It is decided that Sebastian will take London since he can’t have Jace and Clary yet. Jace feels like he still doesn’t have control. Clary points out his progress. She decides to take Emma’s advice and asks him to take her shopping for a real sword.
The pack came to help clean up the dead Endarkened while Joran went to look for Simon. The next morning, Jordan and Maia meet up. she has something to tell him, but decides it can wait until after they find their friend. The Praetor calls and tells him to come to headquarters. Maia agrees to go with him. Simon wakes up in a cage in the Hotel Dumort, dressed like he is on the cover of a romance novel. Maureen comes into the room to tell him that they are finally together. She plans to let him out when he falls in love with her. Simon knows her becoming this monster was his fault. Jordan and Maia arrive at the Praetor headquarters to find it has been burned to the ground; the guards all dead. Jordan finds Praetor Scott’s body. Maia joins him. Sebastian appears and stabs Jordan with his sword. He tells Maia that he will kill all Downworlders that alley themselves wit the Shadowhunters. He tells her that Jordan is dead before he leaves her to spread his message. Magnus sits in the Hunter’s Moon with Catarina, another warlock. She points out that she has never seen him happily in a relationship until Alec. She points out how Tessa proved it was worth the inevitable end. She offers her Council seat to Magnus to go to Idris and shows him Meloirn’s dinner invitation to the Council Downworlders. Bat gets a call and Magnus knows something is wrong. Beat tells him what happened to the Praetor Lupus.
Emma and Julian try to feed the baby, Tavvy. Helen comes up to their apartment-like attic on the London Institute was unsuccessful. Emma and Julian are jealous that their LA Institute hand’t survived. Emma says she wants to watch them kill Sebastian in Angel Square. Helen is horrified, but Julian seems to agree. Jace and Clary go into Diana’s weapon shop. She offers Clary the shorter partner sword to Sebastian’s. She doesn’t want it at first, but Diana points out that fear of the Morganstern name give Sebastian power over her. Diana informs them of the attack on the London Institute and Clary runs out. Jace follows and explains the meaning of Morganstern to her. Raphael comes to Simon with an offer. He wants Simon to go to Alicante with him to tell the Inquisitor about Maureen’s killing spree. The other vampires like the freedom, but Raphael worries about exposure and long term consequences. Without much of a choice, Simon agrees to go. Jace takes Clary to bless her first weapon in the fountain (a Shadowhunter tradition). When they are through, they start talking and Jace admits that he thinks what is happening is his fault for helping Sebastian when they were bound. He thinks he will fall to evil eventually. The demon towers turn to red and gold, signaling that everyone should get to the Gard. Jace is furious when he finds out they are only letting people through to the attack on the Adamant Citadel that have loved ones who have been turned. The Clave want the Endarkened brought back alive to find a cure. Jace tries to tell his adoptive father, Robert, that Sebastian is expecting the Clave’s reaction and only took 20 of his own warriors for a reason. Jace tells Clary that he is going through the portal, and he already knows that she is going with him.
Jace and Clary arrive at the Adamant Citadel and the portal closes behind them. More Endarkened appear. One Shadowhunter tries to talk to her turned brother, but he cuts off her head. More Endarkened appear. jace realizes it is a trap and sends Clary to make a portal to get them out of there. Jace starts fighting. The Endarkened avoid Clary as she makes her way to a wall. She pulls out her stele, but Amatis finds her and tells her to put it away. Amatis starts leading Clary to Sebastian, but gets distracted by Jace cutting down so many Endarkened warriors so quickly. Clary has the opportunity to fight back and is able to get AMatis to the ground and her sword to her throat. Isabelle and Alec race to the Gard when the demon towers signal that they are needed. Robert stops Isabelle from going through. She starts yelling at him. Alec comes along and tries to calm her down, and then Maryse. Isabelle admits that she knows about her father’s affair and that he only stayed around because of Maryse got pregnant with Max. Alec turns and walks away and Isabelle storms off. Jace fights off the Endarkened until Sebastian arrives to challenge him. Sebastian tells Jace that he has Clary, and indicates what he is going to do to her. Jace makes a mistake out of anger and ends up on the ground. Sebastian stabs him in the arm and is burned by heavenly fire. The Iron Sisters surround them and they tell Sebastian to leave. He uses his sword to create a rift in the ground and jumps into it. Alec tries to convince Consul Jia to send help to the Citadel. He suddenly feels Jace’s pain and tells her to open a portal quickly. Clary is thrown off Amatis when Sebastian opens up the earth. Luke’s sister jumps into the rift and Clary races for Jace. He is surrounded by Iron Sisters. Brother Zachariah puts a rune on his hand and presses it to Jace’s wound. Zachariah is engulfed in flames and Jace is left spasming. Clary holds Jace down and puts all of her energy into a healing rune. A portal opens just before she passes out.
Simon and Raphael arrive in Alicante and realize everyone is at the Gard because of the red demon towers. Raphael suggests they go to the house reserved for the vampire Council member when they see Isabelle. She is excited to see Simon and they decide to go inside. Magnus visits Jocelyn and Luke. He determines that Sebastian didn’t do anything to the box he left at Amatis’ house. He also tells them the message Maia gave him from Sebastian. He plans to tell the Downworlders at Meliorn’s dinner. Helen shows up at the door with a message about Clary. Back at the Station, Bat wakes Maia up. He tells her Simon is in Idris. The surviving Praetor, Rufus, is trying to convince the pack to sever their ties with Luke and the Shadowhunters. Maia and Bat know that Sebastian will come after them when he is through with the Nephilim, but other pack members are being swayed. Isabelle goes through Alec’s clothes to get Simon out of Maureen’s costume. They start getting intimate when Alec finds them. Simon changes while Alec fills Isabelle in. Simon is surprised to find out Isabelle was worried about Jace and Clary and didn’t tell him. Alec explains that something is wrong with Jace. Another jolt of pain sends him to his knees; Jace is back in Idris. Alec and Isabelle leave Simon outside of the Basilias (hospital) while they go to see Jace. Raphael comes along and takes Simon to where Jocelyn, Luke, and Magnus are watching over an unconscious Clary. Magnus is healing her while Luke explains to Simon that Jordan is dead. Alec sees Magnus and goes back inside to avoid him.
Clary wakes up and Jocelyn and Luke fill her in on everything that has been going on. Simon appears and also explains his story. Clary realizes that he needs blood and gets ready to take him to the vampire Council’s house. Luke warns Clary that there will be a guard at the house to make sure she is in (and stays in) after dark. Maia attends the funeral for the fallen werewolves. Bat comes up to express his sympathies for Jordan. Maia admits that she was about to break up with him. She feels guilty that he died with her lying to him. Bat explains that it is probably better that he died feeling loved and forgiven. Jace wakes up and decides that he doesn’t need to stay in the infirmary. He asks about Brother Zachariah and refuses to leave without seeing him. Brother Enoch takes Jace to see him and Jace is surprised to see a boy about his age. The heavenly fire burned away his curse and turned him back into a regular Shadowhunter (Jem). He explains that love is what makes Shadowhunters worthy of protecting humans. He plans to go to Tessa, but he has to learn how to be human again first. Simon and Clary make it to the vampire Council’s house. Raphael gives him blood and makes a few comments that makes simon realize that Raphael is jealous of him. The blood turned out to be drugged and Simon becomes drunk, yelling for Isabelle. Clary tires to drag him home, but is unsuccessful until Robert comes out to yell at him. He agrees to talk to Simon at the Council meeting. Clary drags him home, but they don’t make it before dark. She figures that the guard has already gone to tattle on her. She has Simon lie down on the couch before going up to her room. Sebastian is there waiting for her.
Clary can’t move her legs because Sebastian put a binding spell on her legs. He once again explains how they are alike. He gives her another chance to join him. At dinner, the Downworlders and Jocelyn discuss their alliance with Shadowhunters. Magnus is distracted and keeps thinking of Alec. By the time he realizes he is drunker than he should be, it is too late. He opens the door to see Endarkened on the other side before he passes out. Sebastian tires to convince Clary to willingly go with him. She refuses. He gets uncomfortably close and promises that Clary will join him. Jace shows up, mocking Sebastian’s loneliness. He attacks, but when Jace stabs him, Sebastian realizes that Jace doesn’t have control over the heavenly fire. He stabs Jace’s sword through himself before using his ring to disappear. Another werewolf comes along to give Maia clean clothes and warns her to keep quiet about her loyalty to Luke. Maia storms off and tells Rufus that Sebastian will kill them all after he is done with the Shadowhunters. He hits Maia in the shoulder. Bat tells Rufus to leave the pack. Rufus challenges him and Bat accepts. Bat tells Maia to stay away from the pack until everything is settled. Jace and Clary are at the Gard. She tells him what happened before the battle at the Burren. Jace is furious and promises to do everything he can to protect her and make things emotionally easier for her. Clary explains that being with Jace is a small victory over Sebastian. He falls asleep while Clary waits for Luke and her mom.
Jia wakes up Jace and Clary for the meeting and Simon joins them. They find the Lightwoods in the crowd and go to them. In front of the empty Downworlder’s chairs is a message written in angel blood from Sebastian. The Nephilim start discussing what happened and what they should do. One of the Endarkened, Matthias, comes up behind Jia and puts a sword to her throat. He tells them that Sebastian has the council members and will kill them if they don’t give Sebastian his sister and adopted brother. The Shadowhunters start refusing, but Jace offers himself willingly if Sebastian leaves Clary alone. Matthias says both must go. Robert asks for time to decided. Matthias raises his blade and Alec shoots it out of his hand. The dais catches on fire with Matthias in the middle. he gives them two days and disappears. Maia uses the keys Bat gave her to drive Jordan’s truck to his and Simon’s apartment. There is a knock on the door and Maia grabs a weapon before opening it. A vampire named Lily is at the door. She refuses to talk to Maia about vampire-werewolf politics until she is the pack leader. Alec puts an healing rune on Jace for the most efficient healing (parabatai runes are stronger). Jace tells Alec that he will give himself up for Magnus, but won’t risk Clary’s life. Jace recounts when he asked Alec to be his parabatai. Alec tells him not to talk like he is going to die. Jace and Alec join the discussion about whether or not the Clave will meet Sebastian’s demands. Simon is able to give some insight about how the Downworlder’s will react. Jace offers himself again. Brother Enoch and Zachariah join them and Zachariah points out that they will have to hand over Jace in a way that will not be expected to keep any kind of advantage. He also points out that Clary and Jace shouldn’t go to the funeral for the fallen Shadowhunters, but meet up with everyone for the next Council meeting.
Zachariah approaches Jia at her request. She tells him that he has served the Clave long enough and can leave Idris. he explains that he is not ready to see Tessa because he will tell her what is going on and she will want to fight. He would rather stay and fight himself than risk her life. Clary sits while Isabelle braids her hair. She tries to keep it together. Isabelle sees a face at the window and they take the person down. It is Emma. Bat starts to fight Rufus for the temporary leadership of the pack. Just as Rufus is about to land the killing blow, Maia issues her own challenge. Rufus accepts. Maia is able to get the advantage by throwing dirt in his eyes. She thinks about Sebastian and it gives her the strength to kill him. She saved Bat and is the new temporary pack leader. jace, Simon, and Alec are talking when Isabelle and Clary bring Emma into the room. She doesn’t trust the Clave, but she seems to trust them because they help people. She tells them that Jia and the higher ranked Clave members have decided that they must give up Jace and Clary to Sebastian. She also tells them that the Endarkened spoke of Edom as if it were a real place rather than an idea of hell. Alec looks it up and thinks it may be Lilith’s demon realm.
Jace tries to convince his family and friends to let him go alone, but in the end, they convince him that he needs them. Clary makes a portal that takes them just outside of the Fairy Queen’s court. They listen in as the queen talks to Gwyn, the leader of the Wild Hunt. She wants a favor from him because she and Sebastian gave him Mark Blackthorn. Meloirn comes along to speak to the queen alone, but notices the group outside the doorway. They rush in, ready for battle. The queen admits that Meloirn is only half faery and can lie. Alec kills him and Clary seals the entrance with a rune to prevent other faeries from coming. Jace demands safe passage to and from Edom. The queen leads them down a path that forks out into three directions. Alec tells them they each lead to a different place; Heaven (which happens to actually be the mundane world), Faerie, and Hell. Jace has the queen swear that she and her people will not alert Sebastian that they were there. He promises that the fey will bleed for their part in the war. Along the path, they find Mark Blackthorn. He was beaten until he ate the faery food and can now only be released by the Wild Hunt. Clary tells him that his family is alive. Jace instructs him to get a message to the Clave about the fey’s betrayal and sends him off with his witchlight. THey continue to the end of the tunnel and come to a vortex of darkness. THey hold hands to go through together. The queen finds a loophole to inform Sebastian that the small group has left Faerie.
Clary meets her normal looking brother (who has green eyes). She remembers her father, Valentine, being a hero who died in the Mortal War. Luke and Jocelyn named their daughter, Valentina, after his fallen parabatai. Jonathan teases his younger half sister about eating the flowers off of the wedding cake. Clary starts to realize that she is about to marry Jace and wonders where Simon is. Jonathan doesn’t seem to know him. Simon is in a dream-like world where he is a rockstar and dating Clary. When he says he loves her, he calls her Isabelle. Simon throws Isabelle a surprise 22nd birthday part. She is surprised when Max (who would’ve been 15) is still only 9 years old. Alec has defeated Sebastian and his forces and prepares to marry Magnus. As his proud father is about to give a speech, Magnus tells him it is an illusion from entering the demon realm. Alec wakes up and shoots one of his arrows at an approaching demon. Everyone snaps out of it and meets up to find that Jace is missing. Clary runs off to find him and the others follow. Clary finds him on the ground and shakes him, telling him whatever he saw isn’t real. Jace says that he didn’t see anything. He uses the bracelet and a tracking rune to find Sebastian. They realize they can’t leave the way they came and Jace presses them to start moving.
Raphael tries to free Magnus’ hands from the chains restraining him in the cell they share with Luke in Edom. Luke worries about Jocelyn, but Magnus points out that she is leverage over Clary. As Jace, Clary, Alec, Isabelle, and Simon continue on their quest, the Shadowhunters realize that their runes fade faster in this realm. A flying demon attacks Jace and lifts him into the air. Alec and Isabelle do what they can from the ground until the demon is dead (but doesn’t disappear because it is already in its home dimension). Simon points out caves in the distance and Alec agrees they should use them as shelter to rest. The cave they choose has a gate with runes carved into it and the walls. jace opens the gate. he and Clary decide to search on tunnel and Simon and Isabelle the other. Alec is left behind to make a fire. As Bat is showing Maia how to be the new pack leader, Catarina brings Malcolm Fade (High Warlock of Los Angeles) to see her. Maia is informed about the kidnapped council members and Sebastian’s terms. Maia decides it is time to make an alliance with the New York vampires. At the end of Jace and Clary’s corridor, they find a cavern with a lake (which has runes at the bottom). Clary expresses her frustration and Jace gives her some encouragement. Simon reassures Isabelle that he is not in love with Clary and only has eyes for her. She kisses him, but stops when she hears something. Isabelle races to the end of the tunnel. Simon follows and can see a city in the distance. Jocelyn is in her own cell when Sebastian comes to discuss “what ifs” with her. He uses his own stele to communicate with Jia, who tells him they will not give him Jace and Clary. He tells her they have already left Idris.
Emma and Julian have been taking care of the younger kids. They wonder what will happen to Emma since she doesn’t have any family. Julian suggests that they become parabatai so they can stay together. They overhear the Penhallows talking about how Jace and Clary are gone. They hear a window break and find an acorn with a message from Mark to the Consul. Magnus worries about Raphael not being able to fee. He and Luke discuss love. Magnus admits that he’s tried to stay away from falling in love with Shadowhunters, but somehow did with Alec. Maia takes 15 pack wolves to meet with Maureen at Toys R Us. The young vampire wants to make an alliance with the wolves to join Sebastian. Maia agrees and offers Maureen her blood to seal the deal. When she drinks from Maia’s wrist, she turns to ash. Lily explains that it was her plan to have Maia inject herself with holy water. Lily and Maia start an alliance to help the Shadowhunters defeat Sebastian. Jace and clary return to the camp. Alec has set up for them. Alec expresses his confusion about not agreeing with the Clave and gets made at Jace for making fun of him. Simon and Isabelle return and tell them what they found. Alec decides to keep watch and Jace offers to join him. Clary falls asleep. Alec explains his feelings to Jace and the dream he saw when they entered the demon realm. Jace sees something and runs out to find Magdalena. She tells him that he is just like Jonathan/Sebastian and wants to rule over a wasteland. She guesses that was his vision when he entered Edom. He swings his seraph blade and releases heavenly fire to kill the demon impersonating the former Iron Sister he killed.
Alec comes running to get Clary. He leads her to Jace and points out that he is in the fire. She draws a rune on her wrist to make herself fireproof and goes to him. He tells her to get out so he can wait for the fire to kill him. he kisses him and tells him to trust her. She remembers the first rune she ever saw in her head and realizes it is a sword hilt (previously thought to be wings). Alec, Isabelle, and Simon are relieved when the fire dies out and their friends emerge unharmed. Jace explains that he lost control, but now knows how to control the fire. Julian and emma give Mark’s note explaining the faeries’ betrayal. When Jia leaves the room, Emma grabs a file labeled “Carstairs: deceased” and hides it under Julian’s shirt. when Jia returns, she asks them to testify about the note. Raphael and Luke watch Jace’s fire until it dies out. Magnus admits that the realm they are in is one of his father’s. The warlock falls asleep and Raphael tells Luke that they don’t want his father’s help. The New York werewolves and vampires work together to contact as many Downworlder leaders as they can. Malcolm comes along to tell them that Catarina requested them at he morgue with a cage. Sebastian takes Jocelyn to a throne room that looks like the meeting hall at the Gard. He shows two windows; one into Edom and the other into Alicante. Jocelyn realizes that the second throne is for Clary. She dives for Sebastian’s knife, but fails. They see Jace’s heavenly fire flare up.
Clary talks with Simon as the group continues on. Jace starts running and the others follow until the reach a cliff. At the bottom of the chasm is Alicante in ruins. Zachariah sits in a room with the council members to discuss the faeries betrayal. Tessa sent a note from the Spiral Labyrinth to tell them there is no cure for the Endarkened; their souls are completely gone and their organs are fried. Zachariah has a plan to use the fey’s betrayal. As they arrive at what should be the Hall of Accords, Alec reads the Shadowhunter’s story of Edom. An angel came out of a lake to create Shadowhunters. However, they depended on the skeptron to defeat the demons, but ended up failing. Inside the tomb, there is a statue of Jonathan Shadowhunter holding the actual skeptron. Simon points out that it is a trap, but Jace climbs up to get the weapon anyway. The red gem (same stone as the one in Isabelle’s necklace) pulses. There are screams and demons start to fly in and attack. Isabelle is bitten in the scuffle. Alec tires healing runes, but they don’t work. Clary creates a portal that takes them back to the cave. She tries her own healing run, but again it is not strong enough. Simon bites open his wrist and lets the blood fall on Isabelle’s wound. Miraculously, it heals.
Sebastian has food sent to his prisoners before visiting them. He tries to convince them to come to his side. Raphael agrees, but is unable to seal the agreement by killing Magnus. Sebastian stabs Raphael in the heart. Catarina shows Maia, Bat and Lily a demon that is at the hospital where she works. They are unable to kill it without a ruined weapon, but capture it. Lily took video to share with other Downworlders why they need Shadowhunters. The demon tells them Sebastian is attacking Alicante the next night. Clary realizes that Simon hasn’t been eating. She points this out to the others and they all start arguing over who he will drink from. Alec takes him a little way down the tunnel and offers his wrist. They talk awkwardly about their relationships and Alec admits that Simon makes Isabelle happy. Simon bites him and can taste Alec’s death wish, just like he could taste Jace’s when he drank his blood on the boat.
Simon and Alec rejoin the others. A few jokes are made and Alec decides to go take watch. He tells Simon to watch over Isabelle. Jace runs to catch up with Alec to apologize for being reckless again and not considering Alec’s feelings. Alec forgives him and continues on. Jace wakes up Clary in the night to bathe in the lake. They are both excited that they can touch each other without worry, but know they have to keep the secret of the heavenly fire being in Clary’s sword from the others. They discuss how much they love each other and then have sex. Isabelle wakes up. She and Simon say they love each other. They start making out and Alec walks in to find them again. Jia receives a note from Maia warning her that Sebastian will attack the next night. She thinks of the boxes Tessa sent from the Labyrinth.
Jace and Alec return from recon and Jace starts explaining his plan. However, it isn’t very clear by his drawing in the sand. Simon suggests they acquire red gear from a few Endarkened to get through. Jace likes the idea and asks Clary if she can use the same rune she used earlier. Emma goes through the file she stole from Jia’s office and tries to figure out who killed her parents (since the evidence points to someone other than the Endarkened). Helen and Ty come in and Ty points out that the warlocks sent things (iron, salt, graveyard dirt) to fend off Faeries. As planned, Jace, Clary, Simon, Alec, and Isabelle are able to kill five Endarkened and take their red gear to fit in. They make their way to Sebastian’s headquarters at the Gard where he is waiting for them with a room full of demons. Clary creates a small portal that Jace jumps through to get the skeptor and returns the same way. He uses it to kill all of Sebastian’s demons with a bright light. Sebastian runs off. jace and Clary go one way and Alec, Isabelle and Simon go another to find Luke and the others. The Endarkened enter the room and start after them. Jia announces that Sebastian will attack that night and tells the Shadowhunters to prepare themselves.
Emma wakes up to sirens and starts putting on gear to fight. Julian comes in to tell her they have to get the younger kids to the Accords Hall. Emma wants to fight, but Julian convinces her that the children need them more. Jace and Clary find Sebastian drawing runes around himself in the large council room where the two windows reside. Sebastian sends Amatis to get Jocelyn. Jace is able to kill a demon before Sebastian sends him flying. Clary realizes that Sebastian wants to rule hell. She tells him he can have it if he leaves their world alone. He explains that the second throne is for her. Helen leads the Blackthorn children and Emma to the Accords Hall. A faery comes after them, but Shadowhunters have prepared and they are able to use iron items to kill it. Three Endarkened appear and Zachariah arrives to take them out. Luke tells Magnus what he can see from the window. There is a sound at the door and Magnus finally sees Alec. Zachariah gets Helen and the children to safety. He tells Emma that she is needed there to help Julian protect the others and to stay with her parabatai. Sebastian shows Clary what is happening in Alicante through the window. He tells her that if she agrees to stay with him and rule, he will leave her world and close the last gate from Edom to Earth. Alec uses a seraph blade to free Magnus. He sends Luke, Isabelle, and Simon ahead to find Jocelyn and they plan to meet at the keep where they came in. Julian points out the Wild Hunt going across the sky. They can hear what is going on outside and realize that they are all going to die. Luke, Simon and Isabelle find and free Jocelyn. THey start moving to go find Clary. Sebastian explains that he will seal the world and the Endarkened will grow weak without him. The Shadowhunters will have the ability to win. He also promises that her family and friends can stay with her and live. She takes her spot on the throne.
The fight reaches into the Accords Hall. Julian and Emma do their best to protect the others. Emma kills a faery. Ty starts approaching his Endarkened father. Julian throws a blade that lands in his dad’s chest and kills him. Amatis arrives to tell Sebastian that Jocelyn isn’t in her cell. Sebastian isn’t worried as the borders are already closing. Magnus point out that the walls are literally closing in, and that Sebastian would have the power to control all of Edom if he sealed the borders between dimensions. Simon and Isabelle are separated from the others. The building seems to be falling apart strategically to lead them to the keep where they find Jace and then Sebastian. The rest of their party comes into the room and Sebastian points out Clary on the throne. Simon tries to get to her, but a line of Endarkened stop him. Everyone stares at Clary in amazement as Sebastian explains the choice she had to make. Jace appears willing to give her up to him for the cause. Sebastian tells her to kiss him to signify their unity. She reaches up, kisses him on the cheek, and says, “Hail, master,” before stabbing him through the chest with her sword that she put the heavenly fire into. The evil (Sebastian) is burned away until only the dying, green-eyed Jonathan remains. Jocelyn goes to him. He tells Jace where the Infernal Cup is (in the demon he killed earlier) and to throw it at the circle of runes to destroy it. Jace does and the Endarkened collapse. There is a loud cry as the sky turns red. Sebastian explains it is Lilith weeping for the loss of her “children,” including him. The Endarkened on Earth start to fall and the faeries flee. The Shadowhunters rejoice, but Emma is trying to tell Julian to be brave. Jonathan apologizes for al that he has done, including trapping them all in Edom. He tells Clary about a dream he had once (exactly like her vision when she came to Edom). He feels lighter before he dies. Jace has already filled in the others about their secret plan. Clary informs them that they do not have a way home. They vote for Magnus to call on his father, Asmodeus, a Prince of Hell who fell from Heaven with Lucifer. He tells them that he wants an immortal life to send them back home. Magnus is willing to accept that he will die if his immortality is taken. Simon offers his immortality and Asmodeus agrees to take it and make him human in exchange for all of his memories of the shadow world (including all his memories of Clary). He agrees and Asmodeus takes him away. The Shadowhunters are returned to Alicante. Clary finally breaks down.
Emma and Jules are allowed to sit in the Council meeting. It is decided that the Seelie Court will take the punishment the Clave has assigned. They will disband their armies and not carry weapons. Magnus tries to point out that the harshness will brew anger and resentment, but the Shadowhunters ignore it. Helen’s loyalty is called into question because she is part faery. It is decided that she will be sent to work on the wards indefinitely and the search for Mark will be abandoned. the Clave agreed to burn Jonathan’s body to make certain that he wouldn’t come back. Jace goes with Clary to throw the Ashes into Lake Lyn. She mourns for all that she and her loved ones have lost. Jia and Luke discuss what is next. They will use the Mortal Cup and reopen the academy. Maia will take over his pack and his Council seat. Jia tells him that Emma will stay in Idris. Emma, who has been listening in, goes crashing into the room. Julian follows and is furious when he finds out that Emma is supposed to go to the new Shadowhunter Academy. They announce that they will become parabatai so they can’t be separated, though Emma seems hesitant. On the way back to Alicante, Jace stops at the Herondale Manor. He tells Clary that he wants to carry on the family name to honor the generations of Herondales that did good. He doesn’t want the legacy to end with him. Alec is on the roof of the Inquisitor’s house when Magnus approaches him. He wants to be with Alec and hands him a notebook - the first installment of his past. He wants Alec to know him completely. Alec accepts the notebook and makes his decision to be with Magnus. Jace takes Clary home and she goes to her room to find Isabelle waiting for her. Clary recounts the phone call she made to Simon and confirms that he has forgotten them. Isabelle and Clary mourn him together. Maia decided to live in Jordan and Simon’s apartment. Jia sends her the Praetor Lupus seal with indication that she should start the group back up. Julian worries about suddenly having to raise his siblings. Emma tries to comfort him. She tries to tell him why she agreed to be his parabatai, but he falls asleep. Isabelle and Magnus go with Clary while she goes to talk to Simon. He doesn’t remember her, but hands her a flyer before she returns to her friends. She gives Isabelle the flyer before leaving. Isabelle notices the name of Simon’s band: the Mortal Instruments. Magnus promises Isabelle that they will try, but Simon has to want it. Magnus approaches Simon and has Isabelle join him. Simon is confused by Magnus telling him about magic and how he, an ordinary boy, was once a great warrior. Magnus offers him a chance to ascend, to become a Shadowhunter. Jace and Clary are expressing their love for each other when Magnus shows up and says he has something important to show them. Robert approaches Alec. he tells him about his parabatai, Michael Wayland, telling him that he loved him. Robert reacted badly and took in Jace to try to make up for it. He tells his son he is proud of him and that he is a good man. Clary follows Magnus back to the wedding and sees Simon. Magnus warns her that he doesn’t remember everything. She runs up and hugs him. He remembers her now. Magnus and Alec have worked through their issues and decide to spend whatever time they are allotted together. Jocelyn approaches Jace to ask him to play the piano. She has grown fond of him over the past few months. Tessa and Jem watch the descendants of their friends from their previous time together. Jocelyn takes Clary to meet Tessa. Simon asks Isabelle to dance. He dreamed about her at night, knowing that something was missing. He wants to earn her love again. Jocelyn explains that Tessa and Jem performed the protection ceremony on her when she was a baby. Tessa gives Clary a Herondale ring (her son’s) to give to Jace and her copy of the Shadowhunter’s Codex. Tessa gives her some advice about love before she and Jem leave for LA to watch over Emma. Isabelle saw Jem take Church with them. Magnus expresses his fear of impending doom from faery retaliation. Alec comes along to invite him to the lake with their friends. Clary gives Jace the Herondale ring and shows him the Codex.