I will try not to make this long winded...
I have been friendly with a couple for a few years now. I coincidentally went to school with the husband and we went on two or three "dates" when we were about 15, I then ended up working with him after university many years later so i knew him first but now we regularly do things together as couples and I am very close with his wife.
A few weeks ago he called at ours after work to borrow some tools from my OH. His wife was away for work so I invited him to stay for dinner. All very normal. My OH went out to play football and he stayed to watch the end of a film we had put on after dinner. He then randomly starts a conversation along the lines of "do you ever wonder what it would have been like if we had stayed together...." Completely out of nowhere. I asked if everything was OK with his wife etc etc and we had a chat before he left.
fast forward to yesterday and his wife sends me a message saying she can't believe I wouldn't tell her if her husband was trying to cheat on her...I phoned her to try and figure it all out and she says that she had always thought I held a torch for him and that they concocted this plan for him to come onto me (which actually I really don't think you can say he did) to see whether I would tell her?
Tell me this isn't the most bizarre thing you've ever heard? What is the appropriate response to this? I was just on the phone with my mouth open and no idea what to say.