An international safecracker steals diamonds destined for the Reich.
A tip comes in to the Gestapo, warning of an impending burglary at the Paris Ritz. The target is the room of a special attaché to the German Ministry of Production, where a safe contains a cache of diamonds intended for use in arms manufacture. When inspectors Jean-Louis St-Cyr and Hermann Kohler arrive, backed up by a Berlin cop, the safe is intact. But when they turn the dial to inspect its contents, it explodes, leaving the policemen shaken but unharmed, and ruining one of the finest suites in the Ritz.
The burglar has already come and gone, leaving the safe rigged with nitroglycerin as a surprise for his pursuers. His codename is Gypsy, and he has deviled the Reich for years. St-Cyr and Kohler will do their best to unmask him, but as they learned long ago, no crime is simple when the victims are servants of the Thousand Year Reich.