Thor is a German shepherd belonging to a typical suburban family, tirelessly devoted to his human "pack." Then Uncle Ted comes to live with Thor's owners. And the terror begins. For Ted is no longer fully human, and only Thor can detect the Bad Thing lurking within Uncle Ted. Only Thor can sense the horror he is helpless to communicate.
The novel is told almost entirely from the dog's POV. Since Thor is not anthropomorphized, he does not narrate (since dogs don't think in language), and doesn't understand most of what his human family does.