Tobey and his older sister Megan, raised in poverty in Ireland, are abandoned by their mother while Tobey is still a baby. Years later, Tobey sets off for Dublin. He does not return to the village until he learns about the death of his father; when Tobey arrives for the funeral he discovers that Megan has already departed. The story alternates between Tobey's search for his sister, and a series of letters from Megan that document her life in London as an animal rights activist, her marriage and divorce, and her work as a veterinarian on a sparsely populated island in the Philippines. Tobey follows in his sister's footsteps, but when he finally arrives on the island, Megan has vanished. In his effort to unravel the mystery of her disappearance, Tobey discovers a sinister purpose behind the island's dilapidated laboratories and its enigmatic inhabitants.