"Warrior Cats: Into the Wild" is the first book in the Warrior Cats series by Erin Hunter. It follows the journey of a house cat named Rusty who dreams of adventure beyond his home. He eventually joins a group of wild cats known as ThunderClan, where he adopts the name Firepaw and learns the ways of the forest. As Firepaw trains to become a warrior, he faces challenges, including rival clans and internal conflicts. The story explores themes of friendship, loyalty, and the struggle for survival in the wild, setting the stage for the adventures that follow in the series.