All the occupants of a rest home, Adelphi Park, are multi-millionaires. And most of them are refusing to see anyone, including Professor Renter who was due to fly to America with Steed to show off his latest invention. His wife is unable or unwilling to help and, curiously, the neighbour, Madden, another millionaire, is missing.

Michael Dyter, the newly elected MP for South-East Anglia is shot shortly after making his acceptance speech in which he had threatened to expose a major scandal involving the government. Steed knows that the subject of this was the recent theft of a nuclear warhead near London. So was Dyter killed to keep him quiet, and if so, by whom?

Steed's trap for criminal mastermind J.P. Spaggs involves a brilliant plan to steal a million pounds in gold bullion. But when two detectives arrive at Steed's flat and arrest Cathy for Spagge's murder things don't seem to be going to plan.

An incoming missile attack, which is detected by all but one of the country's early warning stations, proves to be a false alarm. Steed finds himself attending an exclusive New Year's Eve fancy-dress party on a train. The train terminates at a remote, deserted station, and a guest is killed with an arrow.

After attending the funeral of an old friend in a lonely Cornish village cemetery, Steed discovers a plot to poison millionaires.

The opposition believe Steed is responsible for the death of their agent Vinkel. Steed, however, had nothing to do with the murder and, as a show of good faith, agrees to a swap of partners with Keller in a bid to find the real killer.

According to Steed's double-agent barber, one of three military men is a traitor. But which one? To find out, Steed becomes a butler, and Emma starts Operation Fascination to trap the woman-hungry Group Captain Miles.