When Steed has a hoard of screaming teenagers rescue his intended victim, spymaster Perov seemingly commits suicide. But days later his system of sleeper agents, the House of Cards, activates, and Steed, Purdy & Gambit find themselves fighting trusted friends.

In an attempt to break Steed's perfect shooting-range record, Purdey tackles the range with all her grace and skill. However, it's not enough as she misses one tiny percentage and gets hit with a mark. But other agents begin to die who have performed similarly, and Steed and Gambit start putting the clues together and find that they must work fast to save their friend and colleague before she succumbs to a nasty poison.

2 scientists are developing a new growth drug which could end world famine. Unfortunately some of the drug has been flushed down the sink resulting in something nasty in the sewers.

Gambit tries to meet Travis, a man carrying some secret film, but he is killed before handing it over.

Steed's plan to have 3 memory experts memorise a third of each of the Allied defence plans for courier purposes seems to have been a perfect success until Juvenator arrives with a machine capable of draining minds.

Mason is the paymaster to a group of informants, but all is not what it seems: the informants are a single man. When Mason suspects this, he is murdered by Wallace, who has been lining his own pockets. Steed begins to investigate, and Wallace decides that the only option left is to frame Steed and kill him.

Paris: Steed captures his nemesis, the Unicorn. But when the Unicorn is accidentally killed by his own men, Steed must use all his cunning to avoid open warfare.

When the Avengers foil a drug drop arranged by a Chinese overlord, they find themselves on the run from his men, the Oriental being determined to have their heads on plates.