The Marquis is a serial killer terrorising London. While the police have no leads the amateur detective Paul Temple (John Bentley) is on the case - this is the last in a short series of Paul Temple films - indeed it's alternative title is Paul Temple Returns. In fact Temple is warned off by The Marquis even before he is on the case which is a bit of an odd move to be honest.
Temple and his wife Steve (Patricia Dainton) obviously arn't put off by these warnings and begin investigating the case even though the police led by Ross (Ronald Leigh-Hunt) are not keen for the help...
Everyone is frightfully posh (apart from a rather dated stereotype Burmese servant) and the film proceeds at a decent tempo with an interesting view of early 1950s London. Paul Temple is a bit bland as a detective and somewhat smug but the film has a good supporting cast including Christopher Lee as a rather creepy Egyptologist and Robert Urquhart.