Basil Sydney and Alastair Sim are two detectives drafted in to investigate the shooting of a gent in his riverside home. It transpires that the murdered man was wealthy, and had entered into a pact with some colleagues whom he had previously badly advised in a business deal, leaving them broke. The terms of this bond were that in five years time, they were all to share equally in any proceeds he had managed to accrue in the intervening years. Our two intrepid coppers - along with a (really annoying) young journalist "Claire" (Judy Gunn) have to try and discover the culprit before midnight strik... lees de rest.