Fifteen-year-old Charles Wallace Murry, whom readers first met in A Wrinkle in Time, has a little task he must accomplish. In 24 hours, a mad dictator will destroy the universe by declaring nuclear war—unless Charles Wallace can go back in time to change one of the many Might-Have-Beens in history. In an intricately layered and suspenseful journey through time, this extraordinary young man psychically enters four different people from other eras. As he perceives through their eyes "what might have been," he begins to comprehend the cosmic significance and consequences of every living creature's actions. As he witnesses first-hand the transformation of civilization from peaceful to warring times, his very existence is threatened, but the alternative is far worse.