A thief has ransacked every room in the Royal Hotel. Old friendships and connections are called upon and Superintendent Bristow of Scotland Yard is called in to investigate. He discovers John Mannering (aka 'The Baron') is a guest, along with his wife, Lorna. Valuable jewellery has been stolen and there is clearly an abiding suspicion – but then comes a mysterious call. A man has two diamonds to sell and also has a very surprising confession to make to Mannering ...