Last weekend was my wife's birthday, we're a couple in our mid 30s with young children so it was nice to have a full weekend to ourselves to celebrate. We took advantage and had plenty of pub time. On our last night in a local pub we were chatting with an acquaintance whom we'd previously known from the same pub, he told us his girlfriend had kicked him out earlier in the day so my wife, Sophie, feeling sorry for him offered him our couch. We'll call him D. Sophie loves to be adventurace, but only in private, she likes to keep her sexual activities very private between the two of us. I've been steadily dropping hints that it wouldn't bother me to see her with another man and that I've a very open view on sex but she's having non of it, told me she'd kill me if I was with another woman. Back to the other night, we all walked back from the pub, we'd been drinking all day, I was just a bit more than merry while S and D were a little more drunk and kept using each other to stop falling over. We got home and S went to get more drinks, but I'd had enough and just wanted to chill watching tv. I could hear S and D in the kitchen knocking back some whiskey we had. They kept going outside for a smoke and getting sillier, laughing at their states, it was all so innocent, like I've seen her get so many times before. Next I heard S telling D that she was married and for M to stop making such remarks, It made me smile knowing he fancied her. S came to sit next to me and pleaded of me to go upstairs with her, I could tell she was very horny, but she's been like this before, I get her upstairs and she collapses on the bed falling asleep and I don't get anything so I told her I'd be up shortly and watched the last 3 mins of my programme while S was getting bedding out for D and ready for me to come to bed. I turned off the Tv and got ready to go upstairs to where I was sure to find S fast asleep but instead when got to the bottom of the stairs I heard the familiar noise, the noise she makes when she's riding my cock. I stood in silence, my heart began racing as I realised D was fucking my wife. I couldn't believe it, and some how I wasn't mad, it turned me on. I didn't know what to do so I went back to the kitchen and turned the light on in a noisy manner, I opened and shut a draw. I heard it go silent upstairs as I loudly closed a door and sorted out the shoes at the bottom of the stairs, I then steadily climbed the stairs to find D on the landing he'd just managed to finish fastening his trousers, I went into the room where we keep our bedding, S was in a corner trying to not draw attention to the fact she was naked from the waist down. She was so drunk she made such a poor attempt of hiding herself, but I didn't let on what I knew and just said I was off to bed. I went to the en suite bathroom and begin brushing my teeth while listening to them talking, he wanted to run, she was convinced I didn't have a clue and that he should stay downstairs as it was too late to go and it would look suspicious. I heard her come into our bedroom and she shut me in the en suite, she must have been trying to hide something, probably that she didn't have her jeans on and she didn't want me to know. Once S was in bed I came out the bathroom, she was under the duvet, I joined her, laying next to her, she stayed still for a few mins until I felt her hand sliding down to my cock. I was hard in seconds and I rolled her onto me. I pushed a finger into her pussy, she was soaked, I knew D must. Have come inside her only a few minutes ago. I let her begin to ride my cock before asking her if she liked D's cock, I asked if he had a big cock and if she enjoyed felling him in her pussy, her eyes shot open, she tried to deny, but I told her what I heard. She said a few things but was to drunk for them to be clear. I told her how much it turned me on and how I wanted her to ride my cock. We both reached a big orgasm together, as I pumped my seed into her pussy to join D's earlier load. S then rolled over and fell asleep. I laid there for a while trying to work out what had happened, what I should be feeling and what I did feel. I woke S up again several hours later, very early morning, maybe 5ish, she was coherent now. I asked her what had happened earlier, she didn't know what I was on about and was shocked at my statement telling her that she'd had sex with D. She told me that she hadn't had any sex, when she learned that we had had some great sex she was shocked before realising that if she doesn't remember sex with me then what else happened? I told her what I'd heard before coming upstairs and what I saw, she knew it must have been true. I told her again how much it turned me on and that I wanted her to suck my cock like she did his. She obliged and brought me to another orgasm this time letting me come in her mouth. She then went down stairs to get a drink. D was awake and she asked him what happened, he quietly told her that she was amazing before she told him I knew. She left him down stairs and came back up to me where we had sex again, she was still in shock. She was so sorry and cannot believe she did it. I told her that its just sex and I was more turned in than anything, she's still struggling to get her head round it but did say that she would be turned on seeing me fuck another woman. I've reminded her that its my birthday soon and it's only fair, I can only hope. Hopefully I can show her this site soon and who knows where that'll lead.