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.
Duval goes to South America to pick up Dave Carson, who is wanted for murder. He walks into the middle of a revolution, and has to work side-by-side with his quarry.
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.
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.
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.
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.
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.
Duval is held up in a small canal town when a strange death occurs. The local authorities think the death is a straight forward suicide, but Duval sees evidence of something more sinister.
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.
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.
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.
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.
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.
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.
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.
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.
A man extorts a large sum of money from an insurance company. Interpol begin a tireless operation to track the man through countries that don't have Interpol agreements.
Author Andrew Slater, writing a book about the war, discovers that Onno van Veer, remembered as a hero of the Dutch resistance, was not executed by the S.S. after all. Duval unearths a tale of treachery and murder.
Duval looks into the slave trading racket, investigating the mysterious disappearance of many thousands of natives from Mombasa during the annual pilgrimages to Mecca.
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.