The Joker

I prefer the Honor Blackman version "Don't Look Behind You".

The only thing about this version is I felt like it was more clear to me that the girl was in league with the man.  (but maybe that was just from having watched essentially the same episode again).

Also, it was more clear that Steed didn't know Emma was in danger and rushed out to help her as soon as he realized (if I recall correctly, the earlier episode implied Steed may have used Cathy as bait and she is rightfully furious at him).

Atmospherically the black & white version worked well for lending extra spookiness, I liked Honor's  portrayal a little more than Diane's.

I'd be curious to know if the episode was shot in the same house.  Seemed similar.