Drama Drama Drama

I don't hold with such carryings on at all, but the question of ratting someone out is a hard one. I've been in that spot and wondered if:

1) I'd be believed
2) If maybe the betrayed spouse already knew on some level and just wasn't ready to deal with it emotionally yet, and I'd be inflicting undue pain by forcing the issue.
3) If maybe the betrayed spouse already knew and was dealing with it and didn't want an outsider stirring things up.
4) If maybe the betrayer was just going thru a phase or something and they'd come to their senses and put things back together except that now I'd blown things sky high.

It truely sucks to be put in the middle that way. As others have said, just tell the REAL friend the truth. If he's REALLY a friend, he'll sort things out and not believe the one who has already betrayed him so badly over the one who did NOT.