When an enemy agent purchases an invisibility formula, the Avengers must find out if the formula's genuine, and if not, how's the apparent invisibility being staged.
The Ministry of Defence had been infiltrated - by an invisible man. The Avengers visit an eccentric professor who claims he sold a formula for invisibility to a pharmaceutical company; actually a front for the Soviets. A pair of spies are in town, and one of them seems to have disappeared. Emma and Steed must discover if he really has the power of invisibility and, if not, how it's being simulated.—don @ minifie-1