The children’s father, Dr. Murry, has mysteriously disappeared. Mrs. Murry insists he will return, but nothing has been heard of him for over a year. He is an astrophysicist working on top-secret projects.
Margaret “Meg" Murry is the protagonist who is continually in trouble at school. Short-tempered, easily frustrated, and lacking patience, she wants to be a part of the gang but does not fit in. Her strength is in her love - familial and romantic - and she is the oldest in the family. Her 10-year old twin brothers are well-adjusted, but her five-year old brother is considered retarded by the town people.
She needs everything to fit neatly into place and make sense, and is frustrated by events she cannot understand. She describes herself as: “A delinquent, that’s what I am, she thought grimly."
Charles Wallace is Meg’s brother – mind reading, and wise beyond his years – he trusts in his intellect. The town views him as an idiot savant, but he considers himself a “sport:" - “an organism that shows a marked change from the normal type or parent stock." He makes friends with three extraterrestrials who help find and rescue Mr. Murry. “It was his mother’s mind, and Meg’s, that he probed with frightening accuracy."
Calvin O’Keefe is the Murry’s neighbor: good-looking, popular at school, and good athlete, but unhappy in his dysfunctional family. At 14, he is older than Meg. His compulsions are really telepathic powers. He loves his mother even though she is indifferent toward him. He has ten siblings: “They all have runny noses. I’m third from the top of eleven kids. I’m a sport."
The villain of the story is a disembodied brain operating on pure logic with no compassion. It controls the inhabitants of Camazotz with its mind, and is part of the Black Thing’s dark evilness.