John Steed's spitting image turns up to complicate things in Two's a Crowd. Or is Steed impersonating someone who just looks very like him?
If you prefer the out-and-out fantastic "spy-fi" side of The Avengers, Man-Eater of Surrey Green is the episode for you
Sherry and biscuits, anyone? Steed and Peel breathe rarefied social air in Dial a Deadly Number, a mystery about business magnates who mysteriously keep dying