Into the Wild (Warriors: The Prophecy Begins #1) by Erin Hunter

FIRE ALONE CAN SAVE OUR CLAN.

For generations, four Clans of cats have shared the forest. But ThunderClan is in grave danger, and ShadowClan grows stronger every dat. In the midst of this turmoil appears a house cat named Rusty . . . who may turn out to be the bravest warrior of them all.