Simon Meets Isabelle at a restaurant for a date. As they start talking, she points out two men that are a vampire’s human subjugates. They introduce themselves as Archer and Walker and tell Simon their master, the leader of the Manhattan Vampire Tribe, has requested to meet with him. He eventually agrees to go, figuring Raphael won’t leave him alone until he does. However, when they arrive (sans Isabelle), he meets Camille. She explains that Raphael usurped her position by framing her fro murder. She wants Simon to go to the Hotel Dumort with her to win back some of the tribe, she offers teach him how to do normal things in return and gives him five days to decide. When Simon gets home, his newly overprotective mother is asleep on the couch. He puts a blanket over her before going to his room to call Clary, remembering he can’t tell her about Camille’s offer.
Clary is alone in the raining room when Simon calls. he tells him that he needs to pick a girl (between Isabelle and Maia) before Jocelyn and Luke’s wedding. Jace comes back and their training becomes less educational. Isabelle comes in and mentions that Maryse in investigating a Shadowhunter that was murdered in Brooklyn. Jace quickly passes over the subject because he doesn’t want Clary to worry. Isabelle tells them she isn’t really interested in anything serious with Simon because he is too boring. Jace walks Clary out and she doesn’t want to leave. He is worried that Jocelyn thinks he will be just like Valentine. He gets oddly emotional before he takes the elevator back up.
While Simon and his friends discuss the pros and cons of having a vampire in their band, a guy named Kyle comes to audition for lead singer. On his way home, Simon is attacked by a man with a knife. Before the blade can pierce his heart, the man is ripped open and turned into salt. When he gets home, his mom has found his bottles of blood. he tries to tell her he is a vampire, but she freaks out. He convinces her with some sort of compulsion that she is dreaming. He packs a bag to leave. With Alec off with Magnus, the Institute has been quite. Jace sits in his room going through Stephen Herondale’s (his biological father’s) things that Amatis gave him. Clary comes over, telling him she snuck out. They start making out and he stabs her with a knife. He has been having this nightmare for weeks and it makes him sick every time. Jace thinks about Valentine and his adoptive brother, Sebastian/Jonathan. He doesn’t want to be like them, but wonders if it is possible to escape Valentine’s influence.
Simon calls Raphael and they meet. He asks his sire about him telling his mom it was all a dream and her believing it. Raphael explains that as vampires, their powers include persuasion. Simon asks if he can stay at the Dumort, but Raphael tells him he can’t stay there until he starts living like a vampire. Jace and Clary go to the park. He falls asleep and wakes up from another nightmare. He says they need to start training and go to a hidden area. The Seelie queen appears to tell them they found a dead Shadowhunter in the park. Jace goes off to call Maryse. The queen questions whether Jace and Clary really love each other, or if they are drawn together because they share the blood of the same angel. When Jace returns, the fairy is gone. Simon plans to stay with Eric, his bandmate, for a few days while he figures out what to do. Kyle comes over to find his keys and offers him a place at his apartment. Simon accepts.
When Simon wakes up in the morning in his new room, Kyle is up cooking breakfast. They have a brief conversation where Kyle doesn’t seem to approve of Simon dating two girls. They go their separate ways. SImon goes to a dress shop with Clary to make sure her dress fits for her mom’s wedding. Maia meets them there to hang out with Simon and asks Luke questions about the party the pack is throwing him. Jocelyn and Clary disappear to see the bride’s dress and Maia leaves. Jace walks in looking for Clary. When she comes out, he acts strangely cold towards her, asking for his jacket and then leaving. Luke, Jocelyn, Clary, and Simon go out to dinner, but it is short lived when the news reports a woman leaving her baby at the hospital with a note asking them to euthanize it. Simon walks home alone and is attacked by two men dressed the exact same as the mugger that attacked him before. Jace lands on one and the other explodes into salt when he tries to shoot Simon. The other disappears and the two boys are left wondering who sent them.
Clary goes to see Jace at the Institute, but he isn’t there. As she waits for the elevator, she realizes that someone is on their way up. Luke appears and Maryse comes along to greet him. They talk about how three Shadowhunters have been found dead in different Downworlder’s territories. Two have been identified as former Circle members. Luke thinks it is a thinly veiled attempt at breaking up the new Accords. Clary sees a rune when Maryse mentions the dead talking. Back in Simon’s new apartment, he notices that Jace looks sick. He takes him to a grocery store to get food. On the way, Jace explains that he was following Clary because he has her phone. He wanted to leave it somewhere she could find it. Simon wonders why he doesn’t just give it to her. While Simon goes to grab soup, Jace is given a girl’s phone number. Simon realizes it happens to him whenever he goes out without glamouring himself. Clary, Luke, and Maryse meet Brother Zachariah in the Bone City. He takes them to the latest Shadowhunter’s body. Clary uses her stele to put the rune on his arm and he seems to wake up. He can feel the pain that was inflicted on him. Maryse starts asking questions and he tells them Camille killed him. Luke uses acid to burn off the rune and let the body rest. He and Clary leave disgusted. Jace and Simon try to figure out who is trying to kill him. Simon tells him about his meeting with Camille, but Jace rules her out because she knows about the mark. Simon goes to get his last bottle of blood and starts drinking it. Kyle comes home and Jace instantly recognizes that he is a werewolf. Luke and Clary ride home in silence. When they do talk, Luke explains that Clary needs to learn more about runes and try to master her powers. She points out that Maryse was supposed to hire someone to help her, but is distracted by Max’s death.
Kyle explains that he is a member of the Praetor Lupus, a pack of werewolves that help out abandoned and newly made Downworlders before they hurt themselves or others. Kyle was assigned to Simon. Jace and Simon fill him in on the attacks, but leave out any mention of the Mark of Cain. When Simon goes to bed, Jace follows, vowing to be his bodyguard. Simon wonders why Jace is going through so much to avoid Clary. Luke calls Simon in the morning, asking to meet alone. Jace is still asleep. When the house phone rings, Clary listens in on her mother’s conversation. Jocelyn plans to go see the baby that was left at the hospital, which died the previous night. She wants to make sure there isn’t someone out there recreating Valentine’s experiments on babies. Clary demands to go with her. Simon sneaks out and meets up with Luke. The werewolf asks him about Camille, explaining she might be involved in the Shadowhunters’ murders. Simon explains his meeting with her. THe next day, she will require an answer, and they will need to find a way to find her to question her. Simon returns to the apartment and tells Kyle and Jace about his early morning meeting. They decide to focus on whoever is trying to kill Simon. THey agree to lure them out after the band performs that night. Kyle is hesitant because he doesn’t know about the mark. Simon questions Jace’s motives for avoiding Clary. Jace isn’t specific in his answer, but seems to want to protect her.
Jocelyn and Clary meet a warlock, Catarina, at the hospital. She takes them to the morgue and opens the drawer with the dead baby. Jocelyn comments that its eyes are just like her son’s when he was a baby. Clary notice’s it has claws for hands. Jocelyn is upset and leaves. Catarina asks Clary to tell Magnus that she showed them what they wanted to see. She also gives her a scrap of fabric the baby was wrapped in. When Clary takes it, she sees a rune. Simon and Jace wait behind stage while Kyle and the rest of the band sets up. Luke and Maryse meet with Raphael’s projection in the Institute’s library. They tell him about one of the dead Shadowhunters, mentioning Camille’s involvement. Raphael tells them he discovered her killing people and told her to leave the tribe. He said she was taking a leave of absence to keep anyone, especially the Clave, from getting suspicious and punishing the whole clan. They ask for his help in capturing Camille to question her, but don’t give him much of a choice in how to answer. Clary arrives at Simon’s gig and finds Isabelle to sit with. She sees Jace hanging around backstage and goes to talk to him. He is surprised to see her since Simon said she couldn’t make it. She tells him to just get the breaking up over with when she realizes he has been avoiding her. He says he isn’t breaking up with her, but can’t talk to her or even look at her. Clary runs outside. Simon starts getting dizzy on stage. He leaves his guitar behind and goes behind the curtain. THe band’s only fan, Maureen, greets him, asking for a picture. He agrees, but ends up biting her.
Jace catches up with Clary and drags her back to the alley behind the bar. He tells her he is watching over Simon so that she’ll forgive him, but she doesn’t know what he did wrong. She tries to get him to tell her what is going on, but he says he can’t live without her and starts kissing her instead. Isabelle finds them while looking for Simon. Jace runs off. Kyle stops Simon from killing Maureen, but when he pulls the vampire back, he is thrown across the room. Kyle tells Simon to wait outside while he takes care of the near dead girl. A lady who claims to be a band promoter gives Simon her card before wandering off. He goes to meet up with his bandmates and sees Isabelle waiting for him. Maia shows up and he is left to explain to both of them what is going on. Kyle comes out and once Maia sees him, she attacks him.
Simon watches as Isabelle pulls Maia off of Kyle, and hold her down until the rage subsides and she starts crying. The Shadowhunter tells both boys to leave. Simon drives them back to the apartment. He starts to pack is bags to leave, but realizes after his own experience with lacking self control, that Kyle had the same issue when he turned. Jordan Kyle admits to all of Maia’s accusations. He joined the Wolf Guard to make up for what he’d done. Simon explains how Maia ended up in Luke’s pack. Clary takes the piece of cloth Catarina gave her and draws the rune she saw on it. The words “Church of Talto” appear on it. Her internet search doesn’t return any results. Clary starts thinking of who can help her. she sends a text with an address and then heads off. Jordan explains that he used to get into fights and was bitten by some guy. A few weeks later, he was irritable and hit Maia. THe night he saw her kiss another guy was his first full moon. The Praetor Lupus found him and explained that he had to join and help others or face punishment. They wouldn’t let him see Maia. The doorbell rings and they find a note threatening someone’s girlfriend at the address Clary is headed to. They call Maia, Isabelle, and then Clary and all seem to be fine. Jordan wants to go watch over Maia. Jace arrives. Clary wanders into the church alone. She finds an atheme on the alter. THere are a series of pictures showing women being injected with demon blood while pregnant. THeir babies are born and they are horrified. Clary goes to leave, but is surrounded by men in grey track suits (like the people that attacked Simon) and a three headed demon between her and the exit.
Clary’s training kicks in and she avoids the demon. She grabs the atheme, but it doesn’t do much damage. She use her stele to draw a rune on it before throwing it at the middle head, which dies. The demon continues after her and beats her to the door. Isabelle shows up and removes the last 2 heads with her whip. Simon goes to meet with Camille under the pretense of joining her. His phone goes off and he disobeys a direct order from her not to answer. He is able to take and send a few pictures before Camille demands he signs a blood oath declaring his loyalty to her. As Simon approaches her, nervous that he will have to follow through, a portal appears and Shadowhunters pour through. Back at the Institute, Isabelle helps heal Clary’s wounds. They talk about Simon being with the Conclave to sort out some vampire politics and how Jace has been acting strangely. Maryse and Jace kill Walker and Archer (it is illegal to have human servants) before Maryse declares the arrest for the murder of Shadowhunters. They take Camille through the portal to be kept in the Sanctuary for questioning. She refuses to talk to anyone except Magnus Bane.
Jace explains to Simon that the Sanctuary was used back before vampires could project their images. Isabelle comes along and they let her know what is going on. She tells them about helping Clary kill a hydra demon. Once Jace learns that his girlfriend is there, he runs off. Isabelle agrees to talk to Simon. She explains that her mom told her about her dad’s affair with another woman and that is why she dates guys who are not willing to commit. Simon explains that heartbreak can make you stronger. When Isabelle learns that Simon broke off his relationship with Clary, she tenses and leaves. Clary wakes up to find Jace by the bed. He kisses her, but she pushes him away. She tells him that he has to talk to her about what is wrong. He explains that the events of Idris are catching up to him. They start making out and he cuts her arm with a knife. She pushes him away and he sinks to the floor. Camille points out that Simon will always be looked down on my the Shadowhunters. They make the vampires repress their predatory nature. Maryse leads Magnus and Alec in. It is obvious that Magnus and Camille know each other; he explains they used to date. Simon can hear Alec and Magnus argue over the warlocks past partners. Eventually Alec leaves and Magnus points out that they will be the only ones left in a hundred years. Simon is overwhelmed by the thought, and leaves as Magnus agrees to talk to Camille for the Conclave. Jace explains to Clary that he has been killing her in his dreams and thinks something is wrong with him. Clary points out that it might be something someone is doing to him. THey decide to go to the Silent City right away. Camille tries to lure Magnus back to her, but he is unwilling. She promises to share information if they grant her immunity. She admits she killed the Circle members under orders from someone much more powerful than herself. Magnus goes to talk to Maryse. The Silent Brothers make a painful intrusion into Jace’s mind. They find out about him dying and the angel, Raziel, bringing him back to life. They say that it is like he is reborn and must undergo the rituals again to be protected. He agrees to stay alone in the Silent City until they can “cure” him. Simon wakes up and Jordan shows him the newspaper that was shoved under their door. Maureen is dead from her throat being cut open. Jordan reminds him that they received a ransom note threatening his girlfriend.
The only place for Jace to sleep in the Silent City is the jail cells. He drifts off to sleep and dreams. Max appears saying the angels sent him with instructions on how to cleanse Jace’s soul from Valentine’s influence. Jace cuts his arms with the dagger from Stephen Herondale. Max collects the blood and draws a symbol on Jace’s chest. Jace collapses in agony. Simon feels responsible for what happened to Maureen. Jordan convinces him to call Jace for help, but Isabelle is the one that answers the phone. Simon tells her what happened. she tells them about the Church of Talto being in the same location. They all plan to meet at Luke’s pack’s party to discuss what to do next. A fairy appears to Clary while she is waiting for the party to start. She gives Clary a bell that she can use to summon someone from the queen’s court. CLary is hesitant, but accepts is. Her mom comes over to check on her because she appeared to be by herself. They talk about Jace before Jocelyn goes back to Luke. Simon and Jordan arrive at the party. Isabelle is waiting for them outside and tells them both to stay away from Maia.
Simon and Jordan join Clary, Alec, and Magnus at their table. Alec still can’t seem to drop not knowing about his boyfriends past and it leads into a verbal fight between them. Alec stalks off. Clary leaves thinking she saw Jace come into the party. Simon follows and Clary tells him most of what has been going on before continuing her search. Maia approaches Simon. She’s mostly forgiven him and he tells her Jordan’s story before going to get some air. Clary finds Jace outside. He claims that the ritual was simpler than the Silent Brothers thought. He questions who he is and whether she would still love him if he was permanently damaged by Valentine’s influence. He asks her to bind them together with a rune and Clary agrees.Jace marks her, but the rune he draws has a much darker meaning. He catches her as she collapses. Magnus tries to talk to Alec, who finally tells Magnus what is wrong. He heard Camille say that Alec looked like Will, a Shadowhunter from Magnus’ past. Magnus tries to explain that his feelings for Alec are unique. Isabelle comes along to tell Magnus that Camille escaped. He needs to help the clave find her so they don’t suspect he had helped her. Maureen comes to Simon as a vampire. She explains that the people who kidnapped her gave her the choice of dying or becoming undead. She tells him they want him because he is a Daylighter. If he doesn’t go, they will continue to hurt people he loves.
Maureen takes Simon to a building that is being constructed. They break in and take the elevator up. Isabelle realizes that Simon is missing. She starts asking around and she, Jordan, Alec, and Maia all look for him. THey decide he isn’t there and to widen their search. Maureen leaves Simon alone on the roof with the woman who claimed to want to promote his band. She tells him that she is the first demon, Lilith. She says that she needs his blood and reveals a glass coffin surrounded by a circle of runes. Sebastian is inside of it suspended in some sort of liquid. The search party goes through the apartment for clues. Jordan and Maia get distracted by their feelings, but end up finding Simon’s wallet. Isabelle finds the band promoter’s business card and gives it to Alec. He explains that the woman’s name is one of the 17 names of Lilith. She was Adam’s first wife and left him and the garden of Eden because she didn’t want to be obedient. God cursed her so that she couldn’t have children, so she created demons in a place called Edom. They decide to go to the address on the card. Lilith wants Simon to turn Sebastian into a vampire so she can start a new race. Simon points out that he cannot revive the dead. Lilith says that since Jace was brought back to life, the dark side is also allotted a life. Simon refuses and starts to walk away until Lilith points out Jace holding a knife to Clary’s throat.
Clary wakes up in Jace’s arms. When she remembers what happened, she tries to get away. She rips Jace’s shirt in the process and sees the red mark on his chest. She realizes that he is under someone’s control and can’t leave him behind. He takes her to the roof. She realizes that Lilith is the greater demon that gave her blood to Valentine to make Sebastian what he became. Lilith demonstrates her complete control over Jace by having him slightly cut Clary. She was the one messing with his head because she needed him present to complete the ritual. When they arrive at the address, Isabelle’s ruby pendant alerts her to demons. They take the elevator to the tenth floor and the ruby goes crazy. They quietly search the floor and find something disturbing. After Lilith explains that Clary had Raziel bring Jace back when he died, Simon agrees to do what Lilith asks to save Clary. Isabelle Looks at one of the many dead babies they have found in a room. she looks at its hands and sees claws, like Clary had described. Isabelle sees something move in the shadows and attacks it. A woman in a grey track suit explains that Lilith saved them. Their babies were too weak to survive her blood and so is the woman. Isabelle goes to the elevator to continue her search for Simon, but when it opens, a mob of track-suited cult members comes after them.
Clary watches as Simon drinks Sebastian’s blood. She tells Jace that she can’t watch and asks to face him. He allows her and she start talking to him, promising a way to save her and obey Lilith. Clary takes advantage of his distracted reaction to her. She grabs the knife from his belt and cuts at Lilith’s mark on his chest. She throws the knife down and tells him to kill one of them. Simon retches up Sebastian’s blood. Alec, Isabelle, Jordan, and Maia fight off the cult members. Alec feels bad for killing the almost-human creatures. One flees and he chases it through a maze of hallways. He ends up finding Camille instead. Jace throws the knife at Lilith and challenges her. She refuses his terms of a fair fight and summons two hell hounds. One goes after him, the other after Clary. Camille tells Alec that she agreed to kill the Shadowhunters because she knew Lilith would kill her if she refused. The mother of demons needed the blood to attempt creating more babies like Sebastian. When Alec refuses to free her, she offers him a way of becoming immortal without becoming a vampire. Alec cuts her free and turns around to see Isabelle, but Camille is already gone. Clary uses the chain holding the Morganstern ring to fend off one of the hellhounds. Jace comes to finish it off after killing the other. He tells her to get out of there. Simon is too sick to focus on what has been going on. He blindly listens to whatever Lilith tells him until Jace starts to fight her. He honestly believes that Clary left, but Lilith pulls her out of hiding. She goes to land the killing blow, but Simon jumps in the way. Her attack is returned to her sevenfold and she turns to salt.
Jace has Simon carry Clary as neither of them have a stele to heal themselves. As they get ready to leave, Alec and Isabelle make it to the roof. They exchange tales of what happened. Isabelle wants to cut Sebastian up, but Simon points out that he is connected to Jace through Lilith’s uncompleted ritual. Alec sends a message to the Clave and Jace agrees to watch over the rooftop scene. Alec pushes Clary out of the elevator to wait with Jace. Maia and Jordan don’t know what happened to Alec and Isabelle. There is a flash of light and Maia grabs him. She kisses him, but can’t explain when he asks why. Clary approaches Jace, angry about how he hasn’t stopped to think about how she has been dealing with his behavior. She explains that none of the night’s events were his fault. They kiss before she goes down to the lobby to find her mom. Simon is surprised that Isabelle came looking for him. They don’t get to talk much before the Clave and Magnus arrive. He watches the warlock and Alec make up. Jocelyn and Luke come running in just before Clary comes out of the elevator. Simon talks to Luke about biting someone. Luke points out that the more he represses his nature, the more it will control him. Simon decides to go home. Simone’s bite woke Sebastian. He controls Jace through Lilith’s healed mark. He finishes binding through blood and the ritual. When it is done, Jace feels at peace.