Recently retired, Carole Seddon resides in the seaside hamlet of Fethering, in the cottage she purchased with her ex-husband. There she maintains a quiet and sensible life with the companionship of Gulliver, her Labrador retriever. But everything changes when she and Gulliver find a corpse on the beach while taking their daily constitutional. What's more, there are two wounds on its neck. The body mysteriously disappears and the police dismiss Carole as a befuddled middle-aged woman. She almost starts to believe it herself—until a stranger threatens her to keep quiet or else.

Unable to contain her anxiety, Carole confides in her eccentric neighbor, Jude, who suggests that if the police cannot be bothered to catch a killer, maybe they should do it themselves.