Exploring New Dynamics in Close Friendships

We swapped partners 1.
This is a true story I have wanted to tell but cant tell anyone else.
My wife and I are in our late 50s.
We played around with 3 sums in our 30s but she put a halt to any other people involved years ago. Sex has been mundane the last 10 years.
My wife worked with a lady (karen)about 10 years younger than us. . They became good friends. She was married to a idiot at the time. We tried going places as 2 couples, but I put a stop to that as I couldn't stand her husband.
Karen is a super sexy lady. I love everything about her. I had the hots for her.
She and her husband divorced a year or so after meeting him.
In the following months 2 times I tried putting the moves on her. Both times she told me NO. She said she wouldnt tell my wife. But to stop making advances on her.
So I stopped. But I still lusted after her and jacked off a lot with her in my imagination.
About 5 years ago. Karen met a guy. We meet him. Loved the guy and we all 4 got along great. She moved in with him.
We as 2 couples do everything together. Weekend trips, 2 week vacations, we have a 2nd home and we are allways there on weekends.
I had seen Mike checking out my wife on many occasions as I still check out Karen ever chance I get.
As a close couple. Karen and I talk on the phone making our plans. As if me and her are a couple.
If we go out, it's not uncommon for her to sit next to me and mike next to my wife. If a stranger seen us. They would think we are the couple.
I started thinking it was strange to be this close with another couple. But we are all good friends.
So all of that bring this story to july 4th.
We went early to our town VFW hall to watch the fireworks. The vfw has a small park setting but adjoining that is the city park. It's pretty big and full of trees.
We had 2 lawn chairs and they brought a big blanked. And a cooler full of alcohol. Several drinks in. We are all feeling good.
My wife and I in the chairs and them laying on the blanket. I got up to walk to the rest rooms across the park. It was dark. The fireworks just started. When I returned mike way in my chair setting next to my wife. So I layed down next to karen on the blanket.