Novelist and amateur sleuth, Paul Temple, meets a newspaper woman called "Steve." Together they investigate a gang of diamond robbers.

A serial killer terrorizes London. Each victim is found with a telegram signed "The Marquis." There seems to be no other common thread between the victims, and Scotland Yard is baffled. Novelist and amateur sleuth, Paul Temple, is warned to stay away from the case, but he and his glamorous wife Steve can never refuse a good mystery.

Paul Temple is called in to help Scotland Yard track down a serial killer who has murdered several wealthy women.

A husband-and-wife detective team look into the murder of one of her friends, whose father--a prominent scientist--has been kidnapped. They find themselves up against a sinister crime organization headed by a mysterious figure known only as "Z".