The Sun Tribe is bound by an ancient law left by the long-vanished Sky People: they must not kill. For other tribes that do not have such a law, the Sun People are easy targets, unable to defend themselves. Their prey is taken, their supplies are emptied, their women are kidnapped and their men are killed. When SunClan priestess Stormy River and her sister are attacked by WolfClan, River fights back and kills their chief's son. Now that the Wolf Tribe has vowed to exterminate all her people, River must do the impossible - prove that she is worthy of being a priestess and find the mythical Sky People.