John Mannering (aka 'The Baron') runs Quinns, an upmarket emporium in London's Mayfair. He is often called upon to solve difficult crimes, but this one is different. 'The Baron' is himself the victim as Quinns has suffered a night time burglary. To make matters worse, a cold-blooded killing has taken place and now he is the suspect. The chase to find the culprits is on and it is a question of who gets there first in the face of both mystery and danger.