A Swiftly Tilting Planet is the third in a series of books referred to as the Time Series: A Wrinkle in Time, A Wind in the Door, A Swiftly Tilting Planet, and Many Waters. Each focuses on different members of the Murry family as they wage battle against the powers of darkness that threaten to dominate the universe.

In the first book, Meg, Charles Wallace, and Calvin O'Keefe journey to the planet Camazotz in the company of three wise women. There they rescue Dr. Murry from the clutches of the evil IT.

In the second book, A Wind in the Door, Meg must help Charles Wallace stop a threatened rip in the galaxy that will destroy Earth. This time, instead of travelling to distant planets, Meg, Calvin, and Mr. Jenkins, the school principal who has caused her so much grief, travel within Charles Wallace's cells to...