Retired gentleman cracksman, John Mannering, (aka "The Baron"), who runs Quinns Antiques in Mayfair, is faced with reverting to his old profession in an effort to save the life of a man accused of murder. The suspense is literally killing and even "The Baron" is not sure of the man's innocence. He gets involved to the point where he too is in danger of being suspected as an accomplice and the reader is kept on edge right up until a very unexpected climax and solution to the mystery is revealed.Once the inheritance of a noble family, the five beautiful jewels of Castille were stolen, separated and their identity lost. Few men could recognize them for what they were, but John Mannering - alias the Baron - was such a man. In pursuit of jewels, Mannering has the misfortune to come up against three of the ugliest criminals he has ever met. To these men, robbery and violence are merely a game, and the Baron an inconvenient pawn who must fight for his life as well as the prize.