The fatal shooting of the much publicized Esmeraldan ambassador shocked London and gave Scotland Yard a dramatic puzzle to unravel. Immediately the Esmeraldan Embassy complicated the Yard's work by holding a suspected Frenchman beyond reach of the police.

This sent Tommy Hambledon of the Foreign Office's intelligence service to Paris and to his old friend Letord in the French Sûreté. Together they set themselves to tracking down the ambassador's dark past and a murderer's present whereabouts.

Just how the crisscrossing clues and numerous suspects tied into the ambassador's death was the big problem to untie before it could snare Hambledon and Letord in new deaths—that could be their own.