The mountain cats followed the sun trail to a new territory, convinced that in a land with more prey, their lives would be free from strife. But while no cat has gone hungry, tensions are rising -- and the once firmly united group has split in two. Caught in the middle is a young cat named Thunder. Orphaned after his father, Clear Sky, rejected him, Thunder has thrived under Gray Wing's watchful eye. But Thunder cannot escape the memory or hurt of his father's rejection. When a devastating fire rips through the forest, Thunder's natural abilities are put to the test. Impressed, Clear Sky invites Thunder to join him. But allegiances borne over time can be stronger than blood ties, and Thunder is forced to decide if he is with his father -- or against him.