Tommy Hambledon is on the track of a major counterfeiting ring. It started when Tommy observed a patron carefully inspecting and then pocketing a circular cardboard mat at a restaurant in Brussels. Intrigued, when the patron left hurriedly and was followed by another man, Tommy joined the procession, unaware that an agent of the Surete was also following. Murder and mayhem take place. Tommy and the French policeman join forces and eventually catch the expert counterfeiters.