Meg Murray has three younger brothers (Sandy and Dennys 10; Charles Wallace 5). The twins keep decent grades at school and seem to be normal. Meg is called unattractive and stupid. Before her father left, he told her that he and her mother had given Meg and Charles tests. They are smarter than normal children, but will develop in their own time. Thinking about her father makes Meg want to cry. She isn’t sure when he will be back and it bothers her that people around town talk about it. She hears the dog, Fortinbras, barking and goes down to the kitchen. Charles is already there and heating up milk for hot chocolate. When Meg checks on the pan, she sees there is enough for two. Their mother joins them and Charles gets up to make both of them sandwiches. Mrs. Murray says she got a call from the boy’s mother that Meg had gotten into a fight with (he had insulted Charles). Mrs. Murray wishes she could help Meg somehow. Charles suggests Mrs. Whatsit might be able to help. He explains she lives in the old “haunted house” and he met her when he was walking Fortinbras and he took off. Suddenly, Fortinbras starts growling at the door that leads to Mrs. Murray’s lab. Mrs. Murray goes to check the door on the other side of her lab that leads outside and comes back with Mrs. Whatsit. She is offered a sandwich and asks for Russian caviar, but Charles denies her because they are saving it for Mrs. Murray’s birthday. Meg makes her tuna salad sandwich. Mrs. Murray helps Mrs. Whatsit take off her books to get the water out, and they both end up on the floor. Mrs. Whatsit admits to stealing Mrs. Buncombe’s sheets (Meg had overheard the ladies at the post office saying a tramp stole them), but insists she can spare them. Before leaving, Mrs. Whatsit tells Mrs. Murray tesseract does exist.
The next morning, Meg wakes up hoping the previous night’s events were just a dream. She goes down to the kitchen where her mother is making French toast and confirms it wasn’t. At school, Meg can’t remember the imports/exports of Nicaragua and gives the teacher an attitude. She is sent to the principle’s office who suggests she faces facts about her father leaving. Meg says she will believe he isn’t coming home when her mother says that is the case. When she gets home from school, Charles is waiting for her. They leave with Fortinbras to visit Mrs. Whatsit and her two friends in the haunted house. Along the way, they meet an older boy, Calvin, who is on the basketball team. He claims he is there to get away from his family, who are mostly sick. He explains that he is a “sport” (has characteristics different from his parents) and gets compulsions occasionally. He followed one to the haunted house. Charles decides he will believe him and invites him to dinner at their house. He accepts and they go into the haunted house together. Mrs. Who is sitting in a rocking chair. She is sewing the stolen sheets into ghosts in case they are needed to scare people away from the house. Charles scolds her for stealing them. She sends them away saying the time isn’t right yet to help their father. They leave and Charles agrees to tell Meg and Calvin what he knows after they have eaten. Calvin admits he feels like he is going home.
When the group arrives back at the Murray house, Mrs. Murray is making stew in her lab so she can keep an eye on it while she works on an experiment. She tells Meg to start on her homework. Calvin admits he has some trouble with math and Meg helps him understand. Mrs. Murray points out that Meg gets frustrated the teachers want Meg to do things the way they teach them when she knows how to do it faster from practicing with her father. After dinner, Calvin goes to read to Charles to put him to bed. Afterwards, Calvin and Meg go for a walk. He asks about her father and she tells him what she knows. He tells her to cry and she eventually does let it all out. He takes off her glasses and tells her she has beautiful eyes. He is glad the glasses will keep others from noticing. Charles arrives with Mrs. Whatsit and Mrs. Who joins shortly after with the stolen sheets. Mrs. Which says she will not waste energy by completely materializing.
Suddenly, Meg feels odd and everyone starts to fade away. She tries to reach out to Charles, but he is gone. Everyone starts to materialize, but no one is able to see Meg. She feels a sudden push and arrives with everyone else on a distant planet called Uriel. Once they are all settled, Mrs. Which tells Mrs. Whatsit to show them. Mrs. Which transforms into a beautiful create with rainbow wings and tells them to get on. She takes them over stone plains and a garden. Charles tries to decipher what the other creatures like Mrs. Whatsit are singing. She has one of the creatures bring each child a flower and they start going up. As the air thins, she tells them to breath through the flower. They come to a flat peak and watch as the sun sets. Mrs. Whatsit tells them not to look at the moon set behind them. Meg drops her flower for a second and can’t breath. Her face lands back in her flower and she is fine. In the distance, there is a shadow. All three children get a bad feeling from it. Mrs. Whatsit takes them back down and they meet back up with Mrs. Which and Mrs. Who. Meg asks if her father is fighting the shadow.
Meg and Charles’ father is behind the shadow and that is where they are heading to help him. Mrs. Who uses a bug to show that a straight line is not the quickest path when you can use a tesser to wrinkle the fabric and bring point A and point B together. That is how they travel. The three women take off and the three children are swept up behind them. They end up landing on a two dimensional planet and the children feel squashed. Mrs. Whatsit quickly reminds Mrs. Which they can’t stay there. They move onto another planet in Orion’s belt. Charles scolds them for the two dimensional mistake, but they promise it was an accident. They lead the children into a cave to meet the happy Medium. She is sitting by a large bon fire gazing into a crystal ball. Mrs. Which has to announce their presence. She asks to show them their home. Reluctantly, she agrees. The crystal ball starts out far away and starts to zoom in on earth, which has a haze over it. Meg asks if it is the atmosphere, but already knows it is the same Darkness they saw on Uriel. Mrs. Which confirms it has been there for years. Though their planet is small and in a small galaxy, many great fighters have come from it. The children list off great thinkers and artists. Meg asks about their father. He is on a planet that has given in to the evil. The children will have to be strong to help him.
The Happy Medium shows them another planet where the Darkness is trying to take over. A star gives it life to fight it off. Mrs. Whatsit did the same thing when she was a star. The Medium insists on showing the children their mothers, but seeing them just makes them sad. They travel to the planet Mr. Murry is on, Camzotz. Mrs. Whatsit gives each child a gift to help them on their quest: Calvin’s enhanced communication, Meg’s enhanced faults, Charles’ resilience of his childhood. Mrs. Who gives Meg her glasses, Calvin a excerpt from the Tempest, and Charles a quote from Goethe. Mrs. Which tells them to go into town and to stay together no matter what. The children start down the path and notice every house is the same. Each has a children either playing with a ball or a jump rope. They all get called inside by their mothers at the same time. One boy drops his ball and is late going in. Charles decides he wants to ask about it. Meg thinks it is a waste of time and they should just continue to look for their father. Calvin reminds them they are not to split up and agrees Charles’ questioning might be useful later. They knock on the door, and a woman answers reluctantly. They ask about her son dropping the ball. She denies it and says they have not had any such issues in decades. Charles hands the boy the ball and he scampers away. The woman insists all their papers are in order and slams the door in their face. The watching neighbors also slam their doors. The children continue down the road and run into a paper boy. He explains that only the boys that deliver the papers are allowed out at this point. He leaves them when he realizes he is behind schedule. Again the children continue into town. They eventually come to the largest building they have ever seen, CENTRAL Central. Charles takes a few minutes to try to reach out to the minds of the people, but he is unable to read them. A man says he is late and rushes into a building. Meg is reminded of the white rabbit form Alice in Wonderland. Calvin says he has a feeling if they go into the building, they will be in great danger.
Knowing they are in danger already, the children go up to the door of the CENTRAL Central building. They don’t see a way in, so Meg goes to knock. The door splits open and they go in. Not knowing where to go, they talk to a man sitting on a bench. He tells them he is going to have to report them for not having their papers. He doesn’t want to, but he has already been processed once and that was more than enough. He takes a paper out of his folder and puts it into the blank wall. A doorway opens into a large room of machines. They make their way through until they come to the end. A man with red eyes is there and talks to them. He doesn’t use his actual voice, but speaks brain to brain. He tries to get them to give into him by reciting time tables. Each child starts calling out different things to keep him from getting to them. Charles says he needs to see what the man is. The blue in his eyes all but disappear and he starts walking towards the man. Meg tackles him. The man is frustrated that they won’t let him take away their difficult decisions to make their lives easier. Meg tells him they might be less hostile if they were fed. He brings out food. To Meg and Calvin, it smells like a turkey dinner. Charles has shut his mind off to the man, so the food tastes like sand to him. After everyone has eaten some, Charles says he has to try again. Calvin agrees. The red eyed man says Charles will be able to come back to himself if he wants, but he doesn’t think Charles will want to. Charles looks into the red eyes. When he asks Meg why she is being uncooperative, she tells Calvin their Charles is gone.
The red eyed man, who says he is the Prime Coordinator, assures Meg that Charles is still there. She realizes both the red eyed man and her brother are being used to speak for IT. Calvin tells her to help him hold on to Charles and they each grab an arm. Meg isn’t able to hold on and charges at the red eyed man, but a guard stops here. Calvin tackles Charles, but three men pull him off. Calvin tells her it is useless and they might as well listen to Charles. Charles tells them the red eyed man and IT are their friend and only want them to be happy. On Camazotz, no one is unhappy because everyone is the same. He points out Meg is miserable at school because she is different. She admits she doesn’t like being different, but she doesn’t want to be like everyone else either. The red eyed man tells Charles to take them to their father. Charles starts walking and Meg and Calvin hurry to catch up. Meg quietly reminds Calvin that his gift is communicating. He tries to get through to Charles and is almost successful. Charles warns them if they keep being uncooperative, he will have to take them to IT. They get into an elevator and Charles explains he opens the seemingly invisible doors by simply moving the atoms and going through the empty space. When the get to the floor, he opens the door and Calvin barely makes it out before closing it. He shows them the boy that dropped his ball earlier. He is being forced to bounce the ball in time and is punished every time he doesn’t. He shows them another room that has a transparent column with their father in it.
Without thinking, Meg runs towards her father. She slams into an invisible wall that separates them. Calvin starts staring down Charles Wallace to try to bring him back. He comes close but ultimately fails. Meg asks him to try her father. Calvin says Mr. Murry cannot see them and continues to try to bring back Charles. Meg uses Mrs. Who’s glasses to get through the wall and into Mr. Murry’s column. They hug and greet each other. Meg realizes her father cannot see her and gives him Mrs. Who’s glasses. He uses them and is able to split the atoms to leave the column. Meg is left alone in the darkness of the column unable to see anything. Mr. Murray comes back in and carries her out. Charles has them all follow him to meet IT. Mr. Murry doesn’t quite believe Charles isn’t himself because his youngest son was only a baby when he left. Meg tells Calvin she feels like the witches betrayed them. Calvin is determined not to give up and goes to keep close to Charles. They come to a large dome building that pulses violet light. Meg try to keep her heart and lungs from falling into its pulsing rhythm. They meet IT, which is just a large brain in on a pedestal in the middle of the room. Meg starts to fall under ITs control, so she starts reciting the Declaration of Independence. Charles tries to tell her Camazotz is equal, but this only makes her realize that sameness isn’t necessarily equality. Her father tells her to list the periodic table elements and irrational square roots. Meg starts to be taken over by IT, so Calvin tells Mr. Murray to tesser. He does and Meg feels like she is being ripped apart.
Meg hears her father and Calvin talking, but they sound distant and frozen. Mr. Murry explains that he was part of a group trying to tesser. They were not able to use animals in their experimentations and drew straws to see who would go first. Mr. Murry drew second. The first man was gone a year before Mr. Murry made his attempt and landed on Camazotz. He was there so long that he was on the verge of giving in to IT before they showed up and rescued him. Meg’s pulse starts to return and she starts to feel less like stone. Mr. Murry massages her hands to help the feeling return. She is under the influence of the darkness and yells at him. She is upset because her father didn’t fix everything. She continually asks where Charles is until they admit they had to leave him behind or else tessering away from IT could have killed her brother. As feeling returns to Meg, she is in pain and starts yelling. Three strange figures with several arms and tentacles all over come over to them. They ask who they are and Calvin explains their predicament. One of them picks up Meg and says they are taking her.
The beasts say they can help Meg and ask Mr. Murry and Calvin to trust them. Seeing no other choice, they do. Meg realizes the beast holding her is incredibly soft and falls asleep in its arms. When she wakes up, she is warm and can be moved. The beast taking care of her tells her she is not healed enough to exert herself yet. She massages, bathes, and feeds Meg. Meg realizes the beast can’t see at all and tires to explain the concept of light and dark to her. She asks what to call her caregiver and the beast searches her head for an appropriate term. She determines Aunt Beast is suitable. Aunt Beast admits it is difficult to communicate with her because their worlds are so different. She says the humans are limited by their sight by what they can see rather than defining things by what they are. Meg falls asleep in Aunt Beasts arms. When they wake up, Aunt Beast takes Meg to have breakfast with her father and Calvin. She is still upset about leaving Charles behind. When she learns they don’t have a plan to rescue him yet, she is even more upset. The beasts don’t understand her feelings. Mr. Murry explains he cannot attempt to teaser again at the risk of being lost in the universe. The beasts have the ability to teaser, but not to a dark planet. Meg and Calvin each try to explain Mrs. Whatsit, Mrs. Who, and Mrs. Which to them. Meg has difficulty trying to define them without visualizing since the beasts cannot see. Calvin says they are angels that watch over them. Mrs. Which speaks to them.
Mrs. Which, Mrs. Who, and Mrs. Whatsit arrive but not in solid form. Mr. Murry introduces himself to them. He is not sure whether or not to trust them. He says he will go back for Charles, but they all know he would just be lost to IT. Calvin volunteers to go because he had almost gotten through to Charles before. The ladies explain that Charles is much further under ITS control since they left. They all agree that Calvin would also eventually be taken over by IT. Meg yells that they can’t make her go. The ladies point out they never asked her to. Meg realizes she is the only one that can save Charles because she is the only one that really knows him. Aunt Beast offers to go with her, but is not allowed. Mrs. Whatsit tells Meg she loves her. Mrs. Who gives her a Bible verse about God’s wisdom and strength. Mrs. Which tessers Meg back through the darkness and to the hill they had started out on before. She tells Meg that she has something IT doesn’t have. Meg automatically starts walking to town. She gets more afraid the closer she gets. She goes straight to the dome building where IT is located. She sees the brain and Charles next to it. She almost gives into IT by hating it. She suddenly realizes IT cannot love. She repeatedly tells Charles that she loves him. He comes back to himself and runs into Meg’s arms. Mrs. Which tessers them home. Meg and Charles land at the same time as Mr. Murry and Calvin. Mrs. Murry, the twins, and Fortinbras are all form a giant hug. Mrs. Which, Mrs. Who, and Mrs. Whatsit are nearby, but have to leave before they can explain why.