Suspected an affair, and caught the guy coming out of her house last weekend after having spent the night. She is renting from another woman who also lives in the house, but the OM was a friend of ours before she moved out. We're separated but not divorced. The guy was evasive, and almost smug when I confronted him. No explanation, no "Hey, you've got the wrong idea", nothing. He had been there both nights over the weekend, and this was while she had my 5yo son there that weekend! She called me withing an hour of my finding out to say that I had the wrong impression, then nothing for 4 days. No explanation at all, said she was too mad.
Last night we talked, rather she talked and I tried to get a word in now and then. She said what her roommate did was none of my business, that I had scared them all by being outside the house, that I was being irrational and creepy, and that she thought we had been getting along fine the past two months. She said she'd spent the week cleaning up the mess I'd created, and said that the reason she hadn't spoken to me before now was that she was a)too mad, b) needed to call the police to see if I had broken and laws (nope!) c)didn't want a confrontation. By the way, I've been nothing but calm and polite with her and OM (YAY ME!!! BIIIG 180!)
She never said that the OM was was dating the woman in her house, just said it was none of my business. She never deined or admitted that she was having an affair, and said that the OM was a friend. At no time during the week did she, the OM, or the woman call to tell me off or correct my impression. Nobody stepped up to say "WTF were you doing, it's not what you think, here's the explanation."