When Jim Qwilleran's friend Polly decides to spend two weeks on vacation with an old girlfriend in Oregon, he finds himself at a loose end—but not for long. A visit from Nick Bamba brings news of a hotbed of mystery. Nick and his wife fear that their new venture, the Domino Inn, won't see out one summer season, let alone a lifetime. A series of fatal accidents on the recently developed Breakfast Island is beginning to deter further visitors, forcing Jim and his cats, Koko and Yum Yum, to scramble for clues.