The Avengers

Season 1, Episode 3

Episode Title: Square Root of Evil

Air Date: 1961-01-21

Overview:

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.