Me and my wife have been together for 10 years. We have been married for 7 of those years. I'm 42 and my wife is 37. We have a little girl who is 5. We both have college degrees and very good jobs. My wife's trademark has always been her ass. When we first met, that was the first thing that got my attention. She is not tall. Her boobs are very average. But, her ass is plump and round. At a party one night, she stood straight up and her sister placed a wine glass on her behind. The glass sat there and didn't even tilt. She knows everybody is always staring at her butt. Last Christmas, we attended a tree trimming party at the house of a friend she works with. I knew most everyone there except for a guy who looked to be around 20 something in age. I asked my wife who he was, and she said that he was the new guy at work. All night long he kept staring at her ass. There was a lot of alcohol at the party and we were all feeling pretty ripe. My wife was feeling no pain and kept staring at Paul- the new guy at work. The only sober human there announced that he was going out to get more alcohol and asked for volunteers to go with him. My wife volunteers me to go with him. I thought- What in hell is she doing? Once outside, I tell the driver that I don't feel so well so I was staying. I was suspicious as hell. So I climbed a tree outside the house so that I could see in the windows. I immediately noticed my wife and Paul talking over in a corner. They were smiling and giving each other the fuck me eyes. A few minutes later, Paul goes upstairs. A little while later, my wife starts up the stairs also. I climb higher up the tree when I see a light come on in one of the upstairs bedrooms. I finally get high enough so I can see in. Paul has his pants unzipped and his cock is sticking out. It's standing strait up. My wife is just sitting on the bed staring at it. He then moves toward her and she reaches out and grabbed his dick. She pulls him close to her head and starts sucking him. I am about to explode in a rage but I'm at the top of a very tall tree and one slip and I'm done for. After a few minutes she stands up and says something to him. He grins like a chesser cat and pushes her over onto the bed with my wife on her stomach. He then lifts her ass high into the air and pulls up her skirt. He then removes her panties. He doesn't even bother with her shirt. Other than her bare ass, she was still fully clothed. He stares at her naked behind for the longest before sliding his cock up her snatch. I'm staring right at her face while he's fucking her. She had her eyes closed and her mouth open. I could tell that she was loving it. Then I see him take his right hand and move it towards her asshole. She then starts biting her lip and I realized that he was fingering her ass. She then turns to say something to him. At that point, he repositioned his cock and pushed it up her ass. My wife started biting the bed sheet. His strokes became faster and he threw his head back with a look of pain. He filled my wife's ass full of cum. She collapsed on her side and I could see it dripping from her stretched asshole. I let them get dressed and go back down stairs. I walked in and acted like I had just returned from the beer trip. My wife noticed that my face was red and that my hands were freezing. A few days later, I told my wife what I had seen. She said that she couldn't remember anything from that night because she was so drunk. I moved out a week later. Three months later she begged me back. She seems to be a new person. She even quit her old job for a new one just to get away from Paul. I still don't know if I can ever trust her again. I can't get the images of the new guy fucking my wife's ass out of my head.