At the offices of the Hatton Garden diamond merchant Duke and Peabody, the body of old Mr Gething is discovered beside a now-empty safe. With multiple suspects, the robbery and murder is clearly the work of a master criminal, and requires a master detective to solve it. Meticulous as ever, Inspector Joseph French of Scotland Yard embarks on an investigation that takes him from the streets of London to Holland, France and Spain, and finally to a ship bound for South America . . .