It is the fifth of the six Thin Man films starring William Powell and Myrna Loy as Dashiell Hammett's dapper ex-private detective Nick Charles and his wife Nora.

When Nick searches Berton's room for clues, he is knocked unconscious by Crazy Mary, a local eccentric.

Several people identify it as part of the specifications for a new aircraft propeller worth a great deal to a "foreign power".

Nick has a souvenir World War II Japanese Nambu sniper rifle belonging to Dr. Clayworth's brother brought in and claims it was the murder weapon.

Then, after proving that the Draques are members of the spy ring, Nick reveals the identity of its leader: Dr. Bruce Clayworth.

Production of a Thin Man film had been planned for 1942, but Myrna Loy refused the role because her attention was focused on her recent marriage to John D. Hertz, Jr. and her all-consuming War work for the Red Cross.

TCM's Notes on the film say that "according to an April 1944 Hollywood Reporter news item, wartime liquor rationing prompted producer Everett Riskin to eliminate the heavy drinking that had been an integral part of Nick and Nora's daily life in previous The Thin Man films".

The Eddie Mannix Ledger, Los Angeles: Margaret Herrick Library, Center for Motion Picture Study.