Firestar's three grandchildren have learned of the powerful prophecy that foretells their destinies, and the responsibility of deciding the Clans' future weighs heavily on the three apprentices. But each secretly yearns for power: Lionpaw dreams of being undefeatable in battle, while Hollypaw longs to be a great leader and Jaypaw knows only he can see the true past and future for them all. Their strengths are tested when ThunderClan is suddenly attacked—and all four Clans are thrown into a battle unlike any the cats have ever seen.

Then a dark shadow falls across the forest, and a mysterious stranger warns the Clans of more trouble to come. For the first time, it appears that StarClan does not hold the answers the cats need.

All of a sudden, the warrior code is being tested. A crisis of faith threatens to tear the four Clans apart and destroy what the cats have built their lives upon.