For generations, four Clans of wild cats have shared the forest according to the laws laid down by their ancestors. But the warrior code is threatened, and the ThunderClan cats are in grave danger. The sinister ShadowClan grows stronger every day. Noble warriors are dying - and some deaths are more mysterious than others. In the midst of this turmoil appears an ordinary housecat named Rusty...who may turn out to be the bravest warrior of them all.

The wild cats of the forest have lived in peace and harmony for many moons - but now, strange messages from their warrior ancestors speak of terrifying new prophecies and a mysterious danger. Brambleclaw, a warrior of ThunderClan, may be the cat with the fate of the forest in his paws. Now, he will need all the courage and strength of the greatest warriors to save the Clans.

Hollypaw, Jaypaw, and Lionpaw - grandchildren of the great leader Firestar - possess unusual power and talent. But secrets and uncertainty surround them, and a mysterious prophecy hints at trouble to come. The warrior code is in danger, and these three apprentices will need all of their strength to help the Clans survive.

As Leafbare approaches, a new danger threatens the Clans. Twoleg construction has encroached on Clan territory, poisoning the stream and making prey especially scarce for SkyClan. Meanwhile, their leader, Leafstar, is struggling with a loss of vision while trying to maintain authority over a Clan that increasingly doubts her ability to lead. In ShadowClan, Tawnypelt senses peril as the Twoleg construction threatens the Moonpool, but she can’t get any cat, especially her son, TigerStar, to listen.

They have always lived by the code—but only change can keep the peace. A new age is dawning on the warrior Clans. Now a new generation of warriors rises—one wrestling with the legacy of his great ancestor Firestar, one seeking to protect her troubled Clan, and one yearning to prove herself as a medicine cat—as leaders from all five Clans agree that the Warrior Code must be reformed.