Cast
- William Gargan as Ellery Queen
- Margaret Lindsay as Nikki Porter
- Charley Grapewin as Police Inspector Richard Queen
- Gale Sondergaard as Mrs. Van Dorn
- Gilbert Roland as Paul Gillette
- Sig Ruman as Heinrich - Spy Leader
- James Burke as Police Sgt. Velie
- Ernst Deutsch as Dr. Morse - Lido Club Physician
- Maurice Cass as Mr. Calkus - Museum Owner
- Minor Watson as Cmdr. Lang
Crew
- James P. Hogan · Director
- Manfred Lee · Writer
- Frederic Dannay · Writer
- Eric Taylor · Writer
- Arthur Strawn · Writer
- Ralph Cohn · Producer
- James S. Brown Jr. · Cinematographer
- Dwight Caldwell · Editor