As Firestar's glorious reign fades into a treasured memory, a new group surges into the Four Clans' territory and takes over. Infamous for their fierce, merciless power and unconditional loyalty, ThornClan resides in a bitter, cold plain, believing StarClan to be superstitious nonsense and living instead by the cruel fist of justice. When WindClan's leader, Willowstar, reluctantly asks for help in stopping ThunderClan from raiding WindClan and stealing their prey, it strikes a chord in Leafstep: and she vows to return balance to the warrior lands.