Warriors (Erin Hunter). Original series

Fireheart, a full-fledged warrior cat, must confront questions of loyalty and identity as he faces the possibility of betrayal from within his own forest clan. Fireheart is a ThunderClan warrior cat now, but danger still lurks in the forest -- and possibly closer than he thinks. With the chill of winter setting in, the cats of rival RiverClan are growing restless, while WindClan is weak and facing threats from all sides. As tensions build to an explosive...

Fireheart, the warrior cat, faces many challenges in his new role of ThunderClan deputy as his apprentice, Cloudpaw, resists following the warrior code, Bluestar weakens, and Tigerclaw continues to haunt the forest seeking revenge.

ThunderClan's darkest hour is upon them and Fireheart, the warrior cat, must protect his clan from a threat unlike any the forest has ever seen, as the time comes for prophecies to unfold and heroes to rise. ThunderClan's darkest hour is upon them, as Tigerstar's quest for power plunges all the Clans into the most terrible danger any cat has ever faced. In order to save his Clan and his friends, Fireheart must uncover the meaning of an ominous proclamation...