Some conmen convince financial journalist Brownley that leading financier Untermeyer is dead. His report throws the stock market into confusion, allowing the conmen to clear up on the markets. Brownley is then murdered.
Duval looks into the slave trading racket, investigating the mysterious disappearance of many thousands of natives from Mombasa during the annual pilgrimages to Mecca.
Duval investigates a murder. The victim's husband appears to have the perfect alibi: he was leading the Italian Mille Migla motor race at the time of her death.
Duval investigates the theft of a million dollars worth of platinum by three men posing as a U.S. Navy Patrol, who killed the passengers and crew of the S.S. Jensen.
Ronald Millais is a gigolo, living off women who fall for his easy charm. Duval investigates claims that Millais has kidnapped a millionaire's daughter.
Schroeder was erroneously convicted of the murder of his business partner, Kaltmann. Duval orders that the ex-convict be watched when he hints at committing the crime for which he has already been punished.
Duval goes to Madrid on the trail of a young couple who have robbed a Tel Aviv bank, using the female's threat to commit suicide as a diversionary tactic.
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.
A policeman is shot in the back in the opal mining settlement of Cranby's Creek, in the Australian outback, and the townsfolk claim the shooting was carried out by Emil Brock, who is wanted for murder by Interpol.
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.
Interpol is called in when the police find the body of a French girl in the boot of an American car. Everything points to Ben Stack as the murderer, but Duval is not convinced.
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.
The driver and hostess of a coach tours company have a profitable sideline carrying out armed robberies in the towns that they visit. Duval investigates the shooting of a Paris jeweler.
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.