'Why the Whales Came' is about ten-year-old Gracie Jenkins, who lives on Bryher, a small island off the western coast of Britain, in the year 1914. "You keep away from the Birdman," Gracie's father warns her. The Birdman lives alone in a cottage that stands all by itself on a hill in the south part of the island. Gracie's father knows stories about him that he thinks are too horrible to tell her. The Birdman used to live on Samson Island, which people say has a curse on it.
Gracie and her friend Daniel have a fleet of toy boats they have made. When the lake where they usually sail the boats is taken over by bad-tempered swans, Daniel talks Gracie into coming with him to a cove near the Birdman's cottage. She's scared, but she finally agrees. Soon they find themselves on the most frightening adventure of their lives.
The whales in the novel are narwhals, a type of whale with a long, spiraling horn on the front of its head. In their adventure, Gracie and Daniel find a narwhal's horn. Later, they have to decide whether to help a stranded narwhal.