Sharona drags a reluctant Monk to a vacation resort down the California coast. His sojourn is quickly interrupted when Sharona's son Benjy witnesses the murder of a woman in one of the rooms through a sightseeing telescope.
The hotel's gung-ho security chief quickly puts the hotel on lockdown, but Benjy's murder sighting soon starts to appear to be a false alarm. The room where the alleged murder took place in is completely spotless, and Sharona thinks her son's imagination may have gotten the better of him. But Monk believes the room is just a little bit TOO clean, and he's convinced Benjy might be on to something.
The room is registered to a Mr. Fenimore, who claims to have been away when the "crime" took place. But his wife is nowhere to be found. Monk is convinced Fenimore murdered his wife - until she turns up alive at her own surprise party several hours later. Maybe Monk needs a vacation more than he realizes.
Trying to get his mind off the murder, Monk and Sharona go see a show. The evening's entertainment: a comedian who finds a career's worth of material with the quirky Monk. But his routine is cut short when Benjy rushes in with terrifying news: he's just found the murdered woman, stashed inside one of the arcade games!
By the time they get to the arcade, the corpse is missing. Benjy can't believe it. Sharona scolds her son for lying, but Monk still believes the boy is on to something. A missing bag of lime soon leads Monk to the hotel gardener, and eventually to a coterie of unusually affluent hotel maids.
Monk soon figures out what happened. The answer was in the spotless condition of the crime scene. Who could have disposed of the evidence so quickly? The maids! The maids were stealing financial information from the hotel's business guests and using it for their own monetary gain. When one of the maids decided she wanted out, she paid the price for it.
But his theory is all mere speculation without a body, which Monk knows is still hidden somewhere in the hotel. He turns the place upside down but finds no trace of any corpse. The maids grin smugly, and it seems that the great detective has finally lost - until a snapshot taken by Sharona when they first checked in provides the answer:
A display in the hotel lobby, promoting a raffle drawing to win a cruise, was adorned with only four oversized steamer trunks when they first checked in. Now, suspiciously, there are five. Sure enough, Monk finds the missing body in the fifth trunk. All in a day's work - or in this case, a day's vacation - for Adrian Monk!