The Globe Travelers Check Co. is faced with financial disaster when Paris is flooded with counterfeit checks. The company that insured Globe against losses by forgery also stands to lose a large sum unless Robin Scott can quickly recover the phony checks and plates. Robin spreads the word through the Parisian underworld that rewards will be paid for information, which results in an informer being killed and Robin barely escaping with his life. Then Robin discovers that the expert forger involved is a supposedly dead man who's very much alive, and is the father of the chief secretary at Globe. Following this lead takes Robin down into the Paris subway where, after a dangerous experience unlocking a locket that's been booby-trapped with high explosives, Robin finally apprehends the forgery gang leader and recovers the checks and plates.
Robin Scott journeys to a small resort in Scotland to run down a man who has embezzled a large number of negotiable bonds. He is told the man he is looking for was there but left. The residents of the resort lodge react to Robin's further inquiries with a hostile suspicious wall of silence that causes Robin to investigate further. He finds the man he is seeking dead and the bonds missing. Confronting the residents with what he has learned, they maintain that the man's death came about accidentally during a fight which he provoked and that they kept quiet about it because the authorities might not look upon the death as an accident. As for the bonds, they insist that they do not know what happened to them. Knowing that one of them is lying, Robin finally tricks the guilty party into revealing where the bonds are hidden.
A $250,000 chalice, used by Christ and his apostles at the last supper, has been stolen from a royal family in exile, living in Portugal's exclusive Estoril area. Only the Queen knew the combination to the palace safe. She and all the other members of the family have far more money than they need, and the chalice is so rare that there is no motive for stealing it. No thief could hope to dispose of it. Robin's problem -- when he repeatedly risks death to solve--is this: How to recover an object which could not have been stolen, and how to find the thief in a family which could not have one.