One night, thirteen-year-old Meg Murry meets an eccentric new neighbor, Mrs Whatsit, who refers to something called a tesseract. She later finds out it is a scientific concept her father was working on before his mysterious disappearance. The following day, Meg, her child genius brother Charles, and fellow schoolmate Calvin visit Mrs Whatsit's home, where the equally strange Mrs Who and the unseen voice of Mrs Which promise to help Meg find and rescue...

Meg Murry and her friends become involved with unearthly strangers and a search for Meg's father, who has disappeared while engaged in secret work for the government.