Steed impersonates Riordan, a forger soon to be released from prison, and gains the trust of gang-leader Hooper. Things seem to be going well until Hooper's second-in-command, known as the Cardinal, announces that Riordan's girlfriend is outside waiting to see him.

Frank Preston is released from prison and is intent on reclaiming the hidden proceeds of his robbery. So is Steed, who has been ordered to follow the man. So are a couple of thugs, who kidnap Carol. So is Preston's scheming wife, eager to get her hands on the one hundred thousand pounds hidden somewhere in the sewers.

Is a creature that can walk up walls clawing to death ruthless and powerful men? Does it have anything to do with Professor Poole's invention of boots that let you walk on the ceiling, or with cartoon superhero the Winged Avenger?

The sudden deaths of several of Steed's former army colleagues are revealed to be part of an elaborate engine of destruction, devised by a man court-martialled by them all. And now he is playing a deadly game.

When agents find themselves in Colonel Mannering's interrogation centre, they think it's a test of their abilities, and relax with drinks when the sessions are over. But who's fooling who. Steed plays catch the pigeon.