Detective Ellery Queen aids Free Dutch agents battle Nazi spies over a prize of industrial diamonds.
| Actor | Role |
|---|---|
 William GarganEllery Queen | Ellery Queen |
 Margaret LindsayNikki Porter | Nikki Porter |
 Charley GrapewinInspector Richard Queen | Inspector Richard Queen |
 Gale SondergaardMrs. Van Dorn | Mrs. Van Dorn |
 Gilbert RolandPaul Gilette | Paul Gilette |
 Sig RumanHeinrich, Spy Leader | Heinrich, Spy Leader |
 James BurkePolice Sergeant Velie | Police Sergeant Velie |