The youngest of the Murry children must travel through time and space in a battle against an evil dictator who would destroy the entire universe. When fifteen-year-old Charles Wallace Murry shouts out an ancient rune meant to ward off the dark in desperation, a radiant creature appears. It is Gaudior, unicorn and time traveler. Charles Wallace and Gaudior must travel into the past on the winds of time to try to find a Might-Have-Been—a moment in the past when the entire course of events leading to the present can be changed, and the future of Earth—this small, swiftly tilting planet—saved.