Meg Murry and her little brother, Charles Wallace, have been without their scientist father, Mr. Murry, for five years, ever since he discovered a new planet and used the concept known as a tesseract to travel there. Joined by Meg's classmate Calvin O'Keefe and guided by the three mysterious astral travelers known as Mrs. Whatsit, Mrs. Who and Mrs. Which, the children brave a dangerous journey to a planet that possesses all of the evil in the universe