One-Ten is convinced that the man is murdered while being interviewed on a live television show was the victim of a hired-killer called "The Teddy Bear." He concocts a plot to trap him using John Steed as bait and Cathy Gale as the woman who wants to hire an assassin to murder him.
Steed and Cathy travel to Marseilles to pick up a flask of a secret new rocket fuel. When they arrive at the airport, they find the bottle gone and their contact dead. The pair battle foreign agents to regain the propellant.
The Home Office becomes concerned when gunrunning to Africa increases and the stockholders of a prominent British gun manufacturer are being murdered one by one. Cathy buys 20 percent of the company's stock to investigate their activities.
A microfilm of North American early warning plans has been stolen and is believed to be somewhere in the luggage of a fading film star. Steed and Dr. King are assigned to retrieve it during a trip across the Atlantic on an ocean liner.
A stamp collector is murdered after he discovers an extremely rare penny stamp being offered for sale on the open market. Cathy takes a job in the stamp collectors store to gather more information, but is unable to prevent a murder in an auction room.
The Home Office is mystified when a diplomatic courier dies defending a satchel full of mundane documents. Steed and Cathy follow a trail of clues from Jamaica to Bogota, Lima and finally to Santiago in Chile to solve the crime.
A Canadian plane crashes under mysterious circumstances in Ireland. Steed's leads take him to the Shamrock airport and a convent, while Dr. King performs autopsies on the dead passengers hoping to find a clue pointing to the wreck's cause.
Cathy Gale impersonates a female assassin in order to get evidence needed to break up an international criminal syndicate. Before Cathy can complete her mission, the real murderess escapes from prison.
A famous astronomer predicts that the entry into the solar system of a small star will result in the destruction of the Earth. Steed and Cathy try to discover the connection, if any, between the astronomer's dire prediction and the threats on his life.
Venus Smith's camera and film are stolen at a fair. When Venus develops the one roll remaining in her possession she discovers she has taken a photograph of a man thought to have committed suicide days earlier.