My wife and I met at work right out of school and dated on and off for over five years. Being young with attractive bodies, we were both a bit wild about sex, mainly because we both attracted attention without much effort from the opposite sex. We would be exclusive for a few months, then one or both of us would start seeing someone else, but each time we would eventually get back together again since no one else could command out attention for long. We finally got married and it has lasted very happily for 20 years. I've strayed a night here or there when on business travel over the years and I've suspected she's used my absences on travel a few times to have a night of fun herself, but we've both followed a 'don't ask, don't tell' policy - after all, modern thought is that men and women are not naturally monogamous, and its just physical sex and doesn't mean anything. Janice, my wife's best girlfriend for all this time got lucky and married someone from their work back then who has made it big in the company over the years, so we're regularly invited to their huge house for parties. My wife has mentioned to me a few times that she's attracted to Janice's husband, and she's told me he's hinted several times over the years that he'd be interested in having her, but she's resisted, mainly because of her friendship with his wife. As a matter of fact, my wife has told Janice each time it's happened and they laugh about it when they meet for coffee and 'girl talk'. We were at theirs a few months ago with about 40 or so other invitees. The drinks flowed freely and the music turned romantic as the evening wore on, so I looked for my wife for some dancing. She was nowhere to be found and Janice soon noticed me looking. She came over and told me her husband was also nowhere to be found. We laughed as we realized we both were thinking the same thing, so she asked, "Shall we explore and see if they are together?" I replied, "What if they are … you know, 'together'?" She gave me a wry smile and said, "We'll cross that bridge if we have to." Leading me to the back stairs to upper floor bedrooms, she continued, "We should do the obvious first and look in the bedrooms." As we reached the hallway at the top of the stairs, a man and a woman came out of a bedroom further down and headed away from us toward the main stairs. We looked at each other with knowing smiles, and she muttered under her breath, "I didn't know we were running a brothel during our parties." We checked each bedroom in turn, but without finding them. I started to breath easier until she led me toward yet another door and told me it was his study. As we approached, there was a sudden series of deep female moans of passion that I recognized as my wife working toward a climax and, as Janice reached for the doorknob, there were the added deep gasps of a man at the same stage of passion. Janice nodded to me knowingly that it was her husband, but we hesitated. She whispered, "We both recognize their voices, so do we need to go in and confront them?" I shrugged my shoulders, "Probably not. We could just wait and confront them when they come out." She thought for a moment and replied, "No, I'm starting to get angry at him for betraying our marriage and your wife for betraying my friendship, so why should we spare them the embarrassment?" Shrugging my shoulders again, I replied, "Well, it doesn't make me angry since she and I have had a bit of fun along the way when we've been apart, but, I've always wanted to see her with another man." Janice looked shocked at me, then gave me that wry smile as she said, "A typical male attitude. He's said that same thing to me, even suggesting it be with you since he knows I'm very comfortable with you." I chuckled and said, "Well, if I had known that, I might have propositioned you myself." She immediately replied, "No you wouldn't have. You wouldn't want to jeopardize my friendship with your wife." I looked at her and asked, "So I guess the idea of seeing him with another woman doesn't make you even a bit horny." She suddenly looked pensive, then said, "I never thought about it before, but I'm starting to like the idea." With that, she turned the doorknob and slowly opened the door. In the few seconds we had loitered whispering to each other before the door, their passion had advanced and, as we stepped inside and quickly closed the door. We could see in the dim light their naked mid-sections slamming against each other as they went over the edge. My wife lay on the thick carpet on her back with her legs spread and wrapped around his back. He lay on her fucking her vigorously, thrusting his cock up her and, from his gasps of passion together with his wild hip thrusts, it was obvious he was coming in her. My wife's mid-section was thrashing around as she arched her jerking hips upward into him. Her arms were gripping his back tightly and her head was thrown back, obviously in the midst of an orgasm. We watched as they worked through their intense mutual climax. One of Janice's hands was gripping mine so hard her nails were digging onto my palm as we stood there transfixed at the sight before us. They didn't notice us as they were lying with their heads furthest from us. When they finished, they stayed in the same position with him on top, his hips still very gently thrusting between her widely spread legs. We had a clear view of his cock still pulsing in my wife's pussy with his cum leaking out around it. This must have been his second come since there was cum smeared in the hair all around her pussy as well as some on the insides of her upper thighs. We stood there silent and still, my cock hard from the sight of them climaxing. Then he started to stroke his cock into my wife more forcefully as he resumed fucking her. She started moving against him and moaned, "Oh, God, yes! Do me again. I can't get enough of your cock." I looked at Janice and she looked at me, then motioned toward the small sofa next to the door and facing them. We silently sat on it, our hips touching and her hand still gripping mine. We watched as their passion resumed and they fucked with enthusiasm. My wife arched her hips up to meet his deep cock thrusts as he urged her towards another climax. He smothered her mouth with passionate wet kisses. Her arms went around his neck as she kissed him back just as deeply. Their kissing seemed to inflame them and heightened their passion. We could hear the moans and sucking sounds their mouths made, as well as the wet squelching sound his cock made as he thrust into her sopping pussy. By this time, my cock was fully erect inside my clothing and, without thinking, I pulled Janice into me and kissed her with an open mouth. She was momentarily shocked, then got a determined look in her eyes and returned my kiss with passion. As we kissed with our tongues exploring with urgency, I placed my hand over her breasts and caressed them through her clothing. When I rubbed her nipples between my thumb and forefinger, they were already hard from her arousal at watching her husband fuck my wife. I was so horny from watching as well as the feel of her body, I wanted her and ran my hand up between her legs under her dress. When she felt my advance, she opened her legs and leaned back, giving me access to her charms. I pushed my whole hand onto her panty clad pussy and roughly caressed her gash through the thin material. I felt her hips roll hard against my hand. I then pushed the gusset of her panties aside and plunged a finger into her cavern, then added another when I felt heat and wetness. She was as hot as me and began thrusting her hips up as I finger fucked her. At this point, we heard the my wife's moans of climax and his gasps as he came in her again followed quickly by the squelching sound made by his cock after he flooded her pussy with another load of hot cum. As I watched them come, I speeded up the thrusting of my fingers up Janice's wet pussy. I felt her body tense and turned my eyes back to her just as her hips started to quiver, then jerk, as she cried out her climax. Her moans and gasps as the waves of orgasm rolled over her caught the attention of our spouses. Janice finished coming as they realized we were there and had watched them come. I pulled my hand out of Janice's pussy just as her husband started to get up from my wife. He stood naked before with a semi-hard cock still dripping cum and demanded to know what was going on. There ensued a ridiculous four-way conversation confirming the obvious. He had the gall to be angry with her for allowing me to finger fuck her and she was furious with him for fucking her best friend. I just sat there amused as I listened to them go at each other. I glanced at my wife still sitting on the floor with her lover's cum dripping out of her pussy. She gave me a wane smile and a little shrug of her shoulders as she nodded toward them, then mouthed 'I'm sorry' to me. I mouthed back 'don't be' and smiled. Relieved at my attitude toward her, she rose and came to me, and sat on the broad arm of the sofa. She leaned against me and I wrapped an arm around her waist. We whispered to each other as they continued having harsh words. She apologized again, but I told her not to worry as it was exceedingly erotic to watch her getting fucked, but insisted I wanted to watch from the beginning if she did that again with anybody. By this time, the argument between Janice and her husband had came to a head and we heard her tell him she was going to let me fuck her in retaliation whether he liked it or not. That caught my attention as did the realization my wife had been stroking my cock beneath my clothing. I was rock hard and extremely horny at the thought of another woman wanting me that way, so I rose when Janice pulled on my arm. I looked at my wife as I did so and she nodded her acceptance. Janice quickly led me to where her husband had fucked my wife on the thick carpet. Pulling her dress up, she removed her panties, then lay on her back with her legs wide open and her hips humping up at me in invitation. I pushed my trousers and underpants down to my ankles and dropped to my knees between her legs. I heard her husband threaten us both, but my wife intervened and told him to stop acting like a fool and sit with her to watch us go at it. I mounted Janice, sliding my respectably sized cock up her very wet pussy. Overcome with the passion of the moment, partly from knowing I was fucking another woman in front of my wife, I thrust hard and deep into her with rapid strokes. She quickly placed her legs behind my thighs and wrapped her arms around my upper back, pulling my body into her with urgency and passion. We proceeded to fuck each other and both of us climbed to the heights of arousal. The image of my wife being fucked by another man played over and over in my mind as I fucked Janice. As fabulous as it felt to be buried in Janice's pussy, it were the images of my wife that drove me toward a climax. All too soon, I felt the cum rushing up my cock. As I gasped out my climax, I gave her a series of hard and deep thrusts of my cock as my cum spurted up her. I continued thrusting into her, trying to help her gain her own climax. She was thrusting her hips hard up into me reaching for her own release. A few seconds later she erupted in a shuddering climax as she gripped me even more tightly with her arms and legs and cried out her satisfaction. I continued to fuck her as she worked through her orgasm. When she was finished, we lay there with me still on top with my cock dwindling inside her pussy until it finally slipped out. We kissed, then rolled onto our sides facing each other and cuddled, kissing some more, oblivious to the presence of my wife and her husband watching us from the same sofa where we had watched them. After we regained our composure, Janice said to me in a low voice that she wanted us to fuck again, then rose off the floor and got rid of her dress and bra. I followed suit, stripping off my clothes. I looked at my wife who had a broad grin on her face as Janice announced that the four of us should retire to their master bedroom where we would sort things out. She grabbed my hand and we made our way there. My wife grabbed her husband's hand and they followed. We entered first and stood by their massive bed where Janice pulled me into her arms and kissed me as she wanked my cock back to a full erection. We took over one half of the bed with her on her hands and knees, ready to be fucked 'doggie'. As I positioned myself behind, her husband and my wife stood nearby and watched as I pushed my rampant cock into Janice's pussy with a single thrust. As I I roughly thrust my cock into her I pulled her hips back into me with my hands each time. My roughness and the depth of my thrusting aroused her quickly and it was only a minute or two before she moaned in passion, then gasped several times before suddenly crying out, "Oh, God! I'm coming! Fuck me! Fuck me hard!" I continued thrusting as her body shuddered and her head whipped about. I slowed down a bit, but when she seemed to finish her climax, I resumed my rough fucking. I had caught the 'fucking frenzy' one reads about and I desperately wanted to dominate the wife of my wife's lover as a way of retaliating against him for his seduction of my wife. I know it now sounds irrational, but it was driving me at that moment. I fucked Janice roughly for another minute or so when she had another short climax, wailing it out as her body again shuddered with her orgasm. I gave her two or three more serial climaxes before my cock could hold back no longer and I came with several shouts of completion as I shot another load of hot cum into the depths of her pussy. We collapsed onto the mattress and panted from the exertion as we slowly recovered. Laying there I felt movement on the mattress near us and watched as he lay on his back and my wife straddled his hips, slowly impaling her pussy on his cock as she slowly lowered herself until it was fully up her. She looked over at me and whispered, "My turn," as she gave me a wicked smile. She fucked him for a long time, alternating rolling her hips with energetic up and down thrusting, several times getting close to coming, then deliberately backing off, then resuming fucking him as she built up to a tremendous climax. He was enthusiastically pumping his hips up into her as well, helping her along. After several minutes of watching them, my wife finally allowed her climax to claim her and literally screamed out as it hit her with unusual force. Her hips quivered, then jerked uncontrollably, as she worked through a long and very powerful orgasm. I had never seen her come like that and it made me horny, like I was watching a highly erotic porn film. Watching them had revived my cock and it was painfully erect, needing relief. I rolled Janice over onto her back and mounted her with a single deep thrust. She wrapped her legs around my back and crossed her ankles. As I started thrusting deep and hard into her pussy, she slid her arms around my neck and arched her hips, and fucked me back. Her passion quickly built and she soon was urging me onward with moans of 'Fuck me' and 'Make me come one more time.' I reached for my climax and when it arrived, she shouted out hers as my frenzied thrusting made her come also. We slammed our hips together as we came almost simultaneously. When we recovered and looked over at our spouses, we saw they had watched us. All of us were momentarily fucked out and looking to rest for a while. I'm not sure who initiated it, but we wound up cuddling and kissing our own spouses. My wife and I soon fell asleep. When we awoke sometime later it was to the movement and sounds of Janice and her husband fucking. We watched and grew horny. When they finished, we made love, then fell asleep until morning. When we awoke, the girls made breakfast and we discussed the situation a lot more calmly than the night before. We've been a swapping foursome since then, but we're allowed to do each other's spouse on a solo basis so long as we announce it beforehand. However, whenever my wife tells me she's going to be with him, I get horny with the image of them being together and call Janice who is usually feeling the same and we get together and fuck. It may be a bit weird, but this arrangement works for the four of us.