A diner collapses and dies in the restaurant's toilet. But when the police arrive the body has disappeared. Soon on the scene are two detectives from the Crime Squad, who have a long standing interest in the dead man, and in his missing car. Crabbe tracks down the car before they do and finds a huge sum of money in the boot.

The 'Happy Ploughman' food chain has won the franchise for the Police canteen, but is being subjected to deliberate vandalism. An obvious suspect is Flora McKee, a local baker who was not only rejected as a supplier to the firm, but was upset by improper advances made to her by its manager, Geoff Reece. Spurred on by Fisher, Henry tracks down the culprit and solves an old mystery into the bargain.