Your story reminds me of an experience we had about ten years ago. Some lifestyle friends of ours had invited us to an on-premise swinger club that hosted a gangbang party on the first Sunday afternoon of each month.
They had a large open room in the back of the club and had placed about fifteen beds in a line a few feet apart in the center of the room, allowing guys to move around the bed and to line up at either the head or foot of the ladies. My wife was nervous and was not sure she would participate, but our friends said they loved it and talked her into giving it a try. The place was crowded, with thirteen ladies and 127 men attending.
We walked into the room, and most of the women were already surrounded by men and taking cocks. My wife walked in naked from the ladies' bathroom and locker room and immediately several guys helped walk her over to an empty bed. She got up on the bed on her back and spread her legs with a line already forming. Within 30 seconds she had a cock in her pussy and another in her mouth as guys surrounded the bed and were rubbing her body while waiting a turn. It was an incredible sight to see and hear as for the next two hours the room was filled with guys fucking the women on the beds.
When things were finished up, the ladies showered and we prepared to leave. As we were walking toward the door out to the parking lot, we ran into my wife's sister's husband. My wife turned fifty shades of red but there was nowhere to hide. He was about twenty years younger than my wife and she always thought he was smoking hot. He had always been very flirty and complimentary to my wife at family gatherings, and I always detected a sexual tension but my wife said I was ridiculous and imagining it. Alan looked right at my wife as we exited and said, "Damn, you made my day, I have always imagined you naked and what it would be like to fuck you, but today you were an incredible fuck. You are so much tighter and hotter than your sister, I hope now we can do it again." I thought my wife was going to die right at that moment.
About five years later, he and my sister-in-law divorced and we have remained close friends with Alan. We never went back to that club for one of their gangbang nights but it definitely created some tension when we saw my sister-in-law and Alan before they divorced.