The island of Anacapa, off the coast of California, is overrun with black rats which are threatening the ancient population of ground-nesting birds. Alma Boyd Takesue of the National Park Service is campaigning to exterminate them once and for all, but her systematic plan is in danger of sabotage by two notorious environmental activists, Anise Reed and Dave LaJoy. But when Alma's sights turn to the infestation of non-native pigs on the island of Santa Cruz - where Anise was brought up by her rancher mother - the stakes are raised and the debate threatens to boil over into something much more real...