Episode #3.2 - S3-E2
Continuity mistake: Humph brags about how he discovered about the affair from a cup of tea; in a wide shot of the whole room he then says "Which is also how I figured out..."; in the background, walking left to right is the same man in cream tank and black bandanna that was already doing the same as an extra earlier in the reveal scene ("It was all a deception, of course") and vanishes in the next shot. (00:43:25 - 00:44:25)