I have Googled in vain for this film, and I am hoping someone on here might remember it.
Definite facts:
The storyline involves a woman whose husband's twin brother is a criminal/killer. He takes her husband's place, but the audience only realises close to the end, when the man you think is the evil twin has been knocked out or arrested or incapacitated in some way. It's a really creepy moment.
It's not 'Dead Ringers'.
Hazy facts:
The actor playing the twins looks a bit like Nick Nolte.
It may be an American made-for-TV type film.
I think it must be 80s or 90s, but it could even have been late 70s. I think I saw it in the 90s and it wasn't modern then.
There might have been a scar involved - there was something that made the woman/the audience suddenly realise that the evil twin had taken the husband's place.
I have remembered it for years and it pops up and niggles me from time to time, so I would be really grateful if someone could name it!