My wife had a secret lover. Well she thought it was a secret. I found out one weekend when we invited a friend around for dinner and then to go to a few pubs. It was actually somebody she knew rather than a friend of mine but we have always got on well and I've known Jim for about 6 months after we'd been introduced. He was an old acquaintance of somebody who she knew from years ago and she bumped into him out shopping one day. He was free that weekend as his wife was away working, so she invited him around so he wasn't on his own. It's not unusual as she has male friends and I have female friends and we have never had a problem with that. Anyway Jim arrived and we had a few glasses of wine with our dinner and he offered to help her with the dishes after we'd finished. As we were quite well relaxed we decided not to go out but stay in and open another bottle. It was eventually time to go to bed and my wife suggested that Jim stay the night in the spare room as he was a little worse for wear, as we all were. I was struggling to keep my eyes open. I showed him the bedroom and we retired to ours. After teeth brushing etc. we went to bed and I heard Jim come out of the bathroom and go into the spare room. My wife was soon breathing slowly as she fell asleep. After about 10-15 minutes I was nearly asleep when my wife asked me if I was asleep. I was close so didn't answer and I felt her get out of bed and saw her dark shape leave our room. I thought she was going to the toilet but didn't hear her go that way. I was now wide awake and silently went to the landing. Jim's door was open as it always swings open if not latched, and I could make out the two of them in bed together. It was very dark where I was but there was some light entering the spare room from street lights outside. I heard them whispering but couldn't make out what was being said. Then I heard them kissing, you know that lip smacking sound. Her head disappeared under the duvet and I could see her body shape near his cock so she was obviously sucking him. He was breathing heavy and gasping occasionally. After a few minutes she pushed the duvet off and then sat on his cock and sighed heavily as it entered her. It was difficult to make out detail but I could see her moving backwards and forwards against him. He was leaning forward obviously sucking her nipples and she gasped and whispered 'oh yes harder'. Within about 5 minutes she suddenly let out a low moan and stopped moving as she came on his cock. As she does with me she stayed still for about 5 minutes and then rolled off and they again started kissing. Without the duvet I could see their dark shapes on the white sheets. They kissed for about 10 minutes, a guess as I had lost all sense of time. I was also as hard as I had ever been and my cock was dripping. She got on her knees and he got behind her and started to fuck her from behind. Her head was in the pillow and he thrust very hard and fast into her. I then realised that this was not the first time as I know that's how she likes it from behind. After quite a long time, where he stopped and slowed several times to stop her from cumming, she told him to keep going and again had another cum. This time she was not as careful to be quiet and groaned loudly into the pillow. He stayed still for the usual 5 minutes, they'd definitely done that before as I know how sensitive she is after a cum and wants to just lay very still. They then lay in each others arms with him on his back and I could just about see her hand playing with his hard cock. From what I could see it didn't look anything special, not huge, or very fat. Just normal, like mine. I was getting cold from just standing but couldn't take my eyes from them. He rolled on top of her and I saw her hands grab his bum and pull him in as he thrust into her. This went on for about 15 minutes and she groaned again as she came. He stopped and lay still and then after they had been whispering for a while he started again and this time was going faster and she was grabbing his bum hard. He suddenly sighed very heavily and she groaned again as he came in her. He thrust another 5 or 6 times as he came in her and then collapsed on her. She lay underneath him quietly waiting for him to recover and then he rolled off and they kissed and cuddled. I thought it was best if I went back to bed to warm up or she would know I'd been out of bed. She joined me about 15 minutes later which was the longest 15 minutes of my life. I wasn't sure if she was going to spend the night with him. I could smell the sex on her as I had turned towards her and pretended to be asleep. She was soon properly asleep but I found it very difficult to sleep but did doze most of the night. About 3 in the morning she again left our bed and went to him. I followed and again watched her with her lover. They kissed and whispered for a few minutes and then he rolled onto her and just started thrusting into her. She came in about 2 minutes and groaned quite loudly and he followed quickly and came, gasping quite loudly, with some very hard thrusts as he shot into her. I returned to bed and she got back into bed soon after. This time she snuggled up to my back and fell asleep with her arm around me. I did sleep for a short while but had a hard on all night. The next morning she got up and went to the loo and I noticed a slightly damp patch where she had been lying. Really didn't know how to deal with it. I was a bit annoyed that she had gone behind my back but had really enjoyed the idea of her cumming with another man although I have no cuckold desires and I waited until Jim had left before I sat her down to chat to her. There were the denials, the tears, the anger that I had watched her, but she said she still loved me and had just got curious about another man as I had been the only one she had been with. After the first time where she said the sex was fantastic, she wanted more and started seeing him about 2 months before. She at first tried to say it was the first time but I explained that he knew what she liked and would prefer to know the truth. As our own sex life had remained good I said that she could continue to see him for sex and he has stayed at ours a couple more times since that night. And I watch, but she always now comes back to me and we have fantastic sex. I think she is starting to tire of her lover and is going to stop seeing him. She has no desire to see other men either and it's a phase that she has gone through.