Lawrence Hammond, a high-powered corporate CEO, is driving his wife to a weekend getaway using the directions given by their car's GPS system when the electronic voice goes haywire, leading them not to a resort hotel but to a deserted lot - a lot where a killer lies in wait. Monk quickly realizes that Erin, the CEO's trophy wife, was the killer's primary target. Her husband was shot only once, and survived just long enough to give a cryptic clue: Girls Can't Eat Fifteen Pizzas. No one knows what it means. Monk pursues the wife angle, and soon discovers that Erin had been having an affair. When Monk sees a sports magazine, he notices that Scott Gregorio, a baseball star, had taken an art class that Erin was also in, and deduces that he was her secret lover.