An unexploded bomb from World War II is found by a dam, and only the makers will know how to defuse it.

Duval investigates the theft of four uncut matched stones from an Angolan diamond mine.

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.

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.

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 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 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.