John Mannering (aka 'The Baron') is a retired jewel thief, known as the best in the business. Nonetheless he is tempted back into his former occupation by an offer from a strange Frenchman who visits him one evening. As a result, he is involved in a search for a famous collection of precious stones that have been smuggled into the country. Having agreed to help, however, he finds himself at odds with his old friend Superintendent Bristow of Scotland Yard, and on the run as The Baron once again .....