Duval investigates the theft of a valuable old master from the collection of Sir Isaac Spendler.

Duval is on the trail of forger Eddie Keflik, who has blackmailed a clown in a traveling circus into working for him.

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.

In Montreal for Interpol's annual conference, Duval catches up with a wanted man who escaped his clutches back in 1939.

The value of paintings by Hugo Ballard begins to soar after his death, so why would his widow slash one of his paintings?

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.

Duval is asked to investigate a gun-running racket in North Africa, and suspects archaeologist Professor Velard of involvement.