Forest of Secrets (Warriors: The Prophecy Begins #3) by Erin Hunter

FIRE ALONE CAN SAVE OUR CLAN.

Tensions are still high among the warrior Clans, and Fireheart is determined to find out the truth about the mysterious death of the former ThunderClan deputy Redtail. But as he searches for answers, he uncovers secrets that some believe would be better left hidden . . .