A few years ago my s/o met another couple and became very good friends. A flirtation developed between myself and the woman in the other couple. My s/o and I fantasized and also had serious conversations about the potential for exploring a sexual relationship between myself and the other woman. A while back both our s/o's were out of town with work, and she came over for dinner and we wound up downing a few bottles of wine. About 3 am we decided to hop in the shower, which led to full blown sex between the two of us. Now, the kicker: my s/o knew what we were doing because I had been texting him and he had given me the ok. I have no idea what, if anything she told her s/o before the event occurred. After words I think she and I were both fairly convinced that we were happy leaving it at that, and not pursuing this side of things any further. Now my s/o is struggling with the situation. We both realize it was a huge drunken mistake, and that we both carry responsibility for what happened, but he cannot get it out of his head. He is not angry with me, just the situation. How do I help him deal with this? We have never had to deal with infidelity before, and are both comfortable with the knowledge that it will probably not happen ever again, I just hate to see him so tormented by his thoughts!