Boredom is dangerous. Jim Qwilleran is bored in Pickax, and makes an impetuous decision to move to the Klingenschoen cabin at the lakeshore in Mooseville, along with his beloved Siamese cats, Koko and Yum Yum. Once he gets there he is frustrated by one problem after another with the heater, leaking gas, the water pipes bursting a huge leak, birds building a nest in his chimney, and host of other maintenance problems with the older building. He subscribes to a repair service, which he calls frequently. All of the people who are dispatched to the cabin are quirky, and some are downright suspicious.
Despite numerous warnings from friends, including one divorced man who claims his marriage broke up because of what Qwill says he intends to do, the stubborn Scotsman decides to build an addition to the cabin. His friends insist that finding a reliable carpenter is next to impossible, and the ‘underground’ carpenters tend to be lazy, unreliable, and their work is questionable.
So when Qwill finds an excellent carpenter right off the bat, he feels that the warnings were exaggerated, and that his addition will go up without a hitch. Everything does go very smoothly - until the carpenter disappears.
Qwill notices a disturbing series of deaths among local carpenters, but no one else makes the connections. Even though he is aware that carpenters are either dying or disappearing, Qwill still complains about the replacement carpenter he finds in public.
In the midst of his carpenter troubles, Qwill and two of his friends go to a small island in the middle of the lake, and are marooned when a storm arises. Worried relatives report the men missing, and they are rescued by a Sheriff’s Department helicopter. Before taking the men to the hospital in Pickax the helicopter pilot surveys the damage done along the lakeshore. The cabin, where the cats are, is safe, but what had been built of the addition has been completely destroyed by a tornado.
A few hours after Qwill gets home following his ordeal, Koko, a remarkable feline, becomes obsessed with the trap door which opens to the crawl space under the cabin for maintenance workers. Qwill investigates and finds that Koko has discovered the body of the second carpenter.
Suspicion falls on the generous, card-carrying good guy, and Qwill is warned to go back to Pickax before some angry local residents take matters into their own hands. A courageous friend stays with the stubborn Jim Qwilleran, just in case there is trouble. Koko leads them to a clue that points them to the real killer, and Yum Yum finds a piece of evidence that proves Qwill’s innocence.