The book begins with a battle between [=ThunderClan=] and [=RiverClan=] over who owns Sunningrocks, a piece of territory smack in the middle of them. When the odds become impossible, Redtail, the [=ThunderClan=] deputy, convinces Tigerclaw, a [=ThunderClan=] warrior, to retreat. In the [=ThunderClan=] camp, Bluestar, the leader, is distraught because [=ThunderClan=] hasn't lost a battle in their own territory since she became leader. The medicine cat Spottedleaf gets a message from [=StarClan=]. She recounts its contents: "Fire Alone Can Save Our Clan." Bluestar trusts Spottedleaf because she has never been wrong before.

Meanwhile, a kittypet called Rusty is hunting a mouse. It turns out to be a dream and he wakes up and decides to go into the woods. His friend Smudge tries to dissuade him, but he ignoresSmudge and starts exploring. While tracking a fox, he is attacked by a forest cat. After a short fight, the forest cat introduces himself as Graypaw. Graypaw tells Rusty about the four Clans. Bluestar and Graypaw's mentor Lionheart appear. Rusty is curious about the clans, and Bluestar tells him that if he is so curious, he can join [=ThunderClan=]. She grants him some time to think. Rusty comes back later and meets Lionheart and Bluestar's nephew Whitestorm. The two warriors take Rusty to the [=ThunderClan=] camp and Bluestar begins to perform the ceremony to make him an apprentice. However, a cat called Longtail notices Rusty's collar and realizes he is a kittypet. Longtail insults Rusty, so they fight, and Rusty's collar is torn off. Bluestar sees it as