I met my wife Lisa at University - she was a petite (5'2) and slim attractive girl with short dark hair, C size breasts that looked bigger on her smallish frame. She was in one of my 3rd year classes and I hit it off with her immediately. We were at University for different reasons - she was there to work hard and build a career, I was there to get by and have a good time. Lisa did party/drink in the weekends and loved going out with her friends and my mates to clubs and pubs - but she was focused on getting in the top 5% of her class and did so at the end of her study. We had a great sex life immediately, she only had three partners before me and had enjoyed sex with each apparently. One of my pub mates (Mike) was a bit of a ladies man, tall and well built from years of rugby - and more than a few of Lisa's friends had shagged him. (I learned later they had told her all about what a good shag he was) but Lisa never really paid much attention to him barring one night towards the end of University. We had been celebrating final exams being over and a large group of us where at a club all pretty drunk. Lisa was looking very sexy with a low riding skirt and a tight button-up top that showed her tits nicely. Towards the end of the night after many drinks - Mike had asked her onto the dance floor, she looked at me, I shrugged and never much into dancing myself said "sure" and with that they had disappeared into the crowd. After about 5 mins I finished my beer and made my way to the bar for a re-fill. The dance floor was lower than the bar and you could look into it, I saw Lisa and Mike towards the back dancing pretty closely. Rather than be annoyed - I was surprised to find that I was turned on to see her being pulled closer to him with each beat of the music until he had her hard up against him with his hands on the small of her back. Lisa was clearly enjoying herself and grinding her hips against his with her arms in the air and staring up to Mike. I moved to get a better view further up the bar and saw him lean close to her say something into her ear to which she just smiled. He took one of her hands and moved it between them placing her hand at the top of his pants. She didnt back away and then I saw her move of arm down a bit - obviously sliding her hand into his pants and feeling his cock on the dance floor. I was amazed at how turned I was instead of pissed off, then watched her proceed to snog him on for the next 5 mins while her hand never left his trousers. After she came up for air from their snogging session and perhaps came to a bit she led him back to our group and acted as if nothing had happened. I didnt say anything and we left soon after for a frantic fuck session at our apartment, she never said why she was so wet or what she had done. I had never seen her act this way before or since and put in down to a "one off" of drink, stress relief from exams and being horny. Fast forward 6 years and we had gotten married lost contact with most of my school friends (including Mike) as Lisa and I got fully into our jobs. The sex was good and sometimes included fantasies about her shagging another guy which turned us both on. Then one day I got an email from Mike saying that he was going to be in town for the weekend and wanted to catch up. We agreed and the three of us met up at a local restaurant for dinner and drinks. Mike hadnt changed, was still good fun, in good shape and there was some obvious sexual tension between Lisa and him. At midnight we called it a night and for some reason (most likely thinking of the night years ago) I invited him to overnight at our house. Lisa agreed it was better than staying in the hotel and we got back to our place for more drinks. Lisa was pretty tipsy at this stage as were all of us and was giving Mike a hard time about what a "bad boy" he was for shagging all her friends - to which he replied that they had hardly been disappointed with his antics. The flirting continued for about about 40 mins before he headed off to the spare room next to ours, with Lisa and I wasting no time stripping of and diving into our own bed. Lisa was very wet and turned on - I started whispering if she had been thinking about joining the ranks of her friends that fucked Mike and had they said what he was like in bed. She replied that he was pretty good by all accounts and had an impressive package plus knew how to use it. Lisa got more and more turned on as I slowly started fucking her, asking her more about Mike. After about 15 mins of teasing her, I was balls deep in her and I asked her if she would fuck Mike and she replied "oh yeah", I then said "well he's right next door - now's your chance". She stopped for a second turned and kissed me hard then slipped out of bed to the door. I thought she was teasing and had actually gone to the bathroom but after 10 mins - she hadn't returned. My whole body was buzzing with the idea that she had actually gone into his room but I was convinced she was still teasing me until I heard a faint but unmistakable "ohhh" from the next door bedroom. I felt like I was going to burst as the moans became louder and clearer accompanied by a slow and constant thumping as if became obvious that Mike was now fucking my wife and she was clearly enjoying it. I had an erection that felt like it was going to explode as I lay there and imagined the scene that was going on next door. For the next two hours Mike fucked my sexy, petite and (until tonight) very straight wife with me laying in the next room listening to all of it. I eventually fell asleep at about 3 AM and was woken up at 7AM to the sounds of Lisa moaning and panting as Mike appeared to be fucking her again and from the sounds of it - she was loving it. After about an hour I heard him dress and leave - then Lisa came in. She was naked, looked well fucked and exhausted - also a bit concerned over my reaction. As soon as she slid into bed, feeling my erection, she smiled and climbed on top of me - sliding my cock into a very wet and loose pussy, proceeding to tell me all about it. Mike had indeed had a large cock and had known how to use it - she had cum many times with him and he had unloaded inside her at least 3 times and she had swallowed his load once. She said it was one of the most intense fucking sessions she had ever experienced knowing I was in the next room and she was fucking a stud that was more than capable of bring her off multiple times. We didn't hear from Mike again and have no desire to repeat the experience - but it was one of the wildest nights I have experienced and we have relived that night many times in bed.