Diamond dealer Jacob Moltz and his accomplice, girl magician Frankie Silver, devise a foolproof plan to rob the biggest diamond house in Amsterdam, and frame safe-cracker Sash Moran.

Insp. Duval is in pursuit of American financier Pearce Clyde, who is wanted for questioning by the U.S. Treasury. When he arrives at Clyde's hotel in the Himalayas, Duval sets off a booby-trap.

Duval responds to a tip-off from an American reporter about a possible organized blackmail racket in a Swiss ski resort and goes to Switzerland posing as his Paris banker friend, Count de Regny. When he arrives in Switzerland he realizes that he has been set up as the next victim.

Lars Lukas, a French swimmer, is shot after completing a cross-Channel swim from France. It appears to be a motiveless murder until Duval hears a tape recording of Lukas's last words, a lead to a smuggling ring.

Duval is on the trail of Thackeray, an international forger who robs safes and substitutes forged bills for the real thing.

Duval agrees to help his old friend, Bernarde, the owner of a Paris salon, to keep his latest creations under wraps until the big fashion show, but Harry Grayson and Mamie Bryant have other ideas.

Duval is called in after an assassination of an American diplomat. Evidence seems to point to a recently released Nazi seeking revenge. What does puzzle Duval is how he constructs the assassinations.