The Harts suspect a college fencing champion of being behind a murderous drug ring. Jonathan fights a razor-sharp duel with the sadistic student.

Industrial espionage is a problem at Hartoy company. When the investigator Jonathan has hired is murdered, the Harts go undercover in an attempt to foil the crooks and save the company from financial destruction.

The Harts visit the gallery of a well-known stamp collector to see the Vermillion, the most valuable stamp in the world. The Harts inadvertantly gain possession of the stamp and their lives are in danger.