High schooler Meg Murry is a social misfit who lives with her mother, twin brothers Sandy and Dennys, and precocious four-year-old brother Charles Wallace. Although she has a high IQ, Meg gets poor grades at school, fights with the other students, and is frequently in trouble.
Mr. Murry has been missing for months, following an attempt to tesser, by traveling through a wrinkle in the space-time continuum.
Three creatures, Mrs. Whatsit, Mrs. Who, and Mrs, Which, take Meg, Charles Wallace, and Calvin to several different planets by tessering. They show the children the evil force threatening Earth and bring them to the planet Camazotz, where the Dark Thing has imprisoned Mr. Murry.
Meg, Charles Wallace, and Calvin find Mr. Murry who is trapped by the Dark Thing, represented on this planet by IT. Meg manages to free her father, but loses Charles Wallace to the power of IT.
Meg returns to Camazotz alone and uses her love for Charles Wallace to break his connection with IT.
I love you, Charles!
Meg, Calvin, and Charles Wallace tesser safely home to Earth with their father.