<p><a href="https://www.patreon.com/beccabellamy/posts?filters%5Btag%5D=summer%20rental">Click here</a> to read the previous parts of the story.</p><p><img data-media-id="167267895" src="/2f/00/2f0078b07eafd6c8c0337b6fdb01cc83e66df680ba88c974b212df0560635b13.jpg"></p><p>Christian woke up a little bit before sunrise and he couldn't get back to sleep, and not for lack of trying. His brain just wasn't interested in letting him return to a restful state, so he got out of bed and headed for the kitchen. If he was up, he was going to make coffee.</p><p>As soon as it was brewing, Christian turned towards the windows and took in the surprisingly beautiful view of the sunrise. The lake was bathed in orange light and it looked impossibly peaceful, as Christian assumed it almost always did in what was typically the quietest part of the day, before most living things had risen from sleep and began their daily routines.</p><p>Christian returned to the kitchen to pour himself a cup of coffee and he heard someone coming downstairs. He felt bad - thinking the sound of the grinder of even the smell of the coffee had woken someone up - but when his sister came around the corner and into the kitchen he couldn't help but smile. He liked the idea of having a little company as he watched the sunrise.</p><p>"Did I wake you?" he asked.</p><p>Marie shook her head. "No. I was up when I smelled the coffee. I figured that meant someone else was up, so there was no reason not to drag myself out of bed." She poured herself a cup, stirred in a little sugar, and then gestured towards the deck. They walked out, sat down, and stared out at the water, which still looked remarkably beautiful as the sun began to peak over the horizon.</p><p>"So, if I'm not mistaken, we both got laid last night," Marie said.</p><p>Christian nearly spit out his coffee, leading to a burst of laughter from his sister.</p><p>"Sorry. Is that not something you expect to hear from your sister?" she asked.</p><p>"I guess not," he replied. "As I very nearly choked on my coffee. But, I won't argue with you. I'm pretty sure you're right, that we both got laid last night." Christian had certainly enjoyed fucking his wife - whose pussy was filled with his brother-in-law's cum while they had sex - and he'd heard Marie's faint moans before he fell asleep, so it wasn't surprising that she'd gotten lucky too. The surprising part was that she'd want to talk about it.</p><p>"There's something about vacation and sex, isn't there?" she observed. "Something kind of wonderful."</p><p>Christian did not know his sister to be particularly contemplative about sex, but it seemed that she was in that kind of mood. "It's almost always better, at least in my experience. Vacation sex, that is. I couldn't really tell you why, but it seems to be the case."</p><p>"Are you saying that the sex you and Ruby had was good?" Marie asked.</p><p>Christian turned and studied his sister's face for a few moments, as he couldn't help but feel like there was something different about her. They hadn't spent a great deal of time together in recent years, so it was possible she'd changed - people do change - and he just hadn't noticed, but this change seemed considerable.</p><p>"Yes, that's what I'm saying," he answered. "Are you saying that the sex between you and Adam was good?"</p><p>Marie looked at the lake with a dreamy smile on her face and said, "I'm saying that I've been having the best sex of my life this week, and in the few weeks before we left for the trip."</p><p>"You know, I've been having the best sex of my life in recent months too," Christian noted. "I guess we're both just lucky, aren't we?"</p><p>Marie nodded and sipped her coffee. Her lips curled into a slight smile as she swallowed and Christian couldn't help but think that there was something she wasn't saying, something that might go a long way towards revealing why she seemed so different.</p><p>"Oh, hey, Ruby and I were talking yesterday about doing something together as a group today. We did some research and decided we should try one of those tubing expeditions where you float down a river, drinks beers, and hang out, or rent bikes and try out that bikeway, which runs through the woods for miles and miles and miles and is apparently absurdly beautiful," Marie said in a sudden change of topic.</p><p>"Yeah, both of those sound great," Christian replied. "We still have plenty of time left here. Why don't we do both?"</p><p>Marie raised her mug, smiled, and said, "I like the way you think, Christian. I wasn't kidding about drinking on the river, either. You'd think that would be strictly against the rules, but apparently there's one company that will let you do just about anything if you sign a waiver. You just have to bring your own drinks and cooler. They'll even give you a smaller tube so you can float the cooler down the river with you."</p><p>Christian laughed. "Seriously?"</p><p>Marie nodded with a big smile on her face. "Absolutely. It's like you're own little booze cruise, and while I know neither of us are really big drinkers, that honestly sounds like a lot of fun to me."</p><p>"Me too," he replied. "I mean, why not, right? We're on vacation. Let's get buzzed and float down a river."</p><p>"How would you feel about heading out to get us a cooler and some drinks?" Marie asked. "That way we can start floating before noon."</p><p>"Sure," Christian said. "When do you want to leave?"</p><p>Marie smiled. "Actually, I was thinking I'd slip into bed with Adam to see if he's in the mood for another round of fun. How would you feel about going alone?"</p><p>Once again Marie managed to surprise Christian with what felt like a new sense of openness regarding sex. It amused him more than anything, though. "No problem."</p><p>"Today is going to be a good day," Marie said as she turned her attention to the lake once more. Her lips slowly curled into a smile and she added, "A very good day."</p><p><img data-media-id="167267902" src="/2f/00/2f0078b07eafd6c8c0337b6fdb01cc83e66df680ba88c974b212df0560635b13.jpg"></p><p>Christian was halfway to the store when he realized he'd forgotten his wallet. For a moment he thought it wouldn't be a problem, but then he remembered that Apple Pay wasn't an option. He'd need a credit or cash to buy anything at the local store. He gripped the steering wheel tightly, took a deep breath to let out some of his frustration, and turned the car around to head back to the house.</p><p>Christian was greeted with a moan of pleasure the moment he stepped into the house. It seemed that Marie had been successful in convincing Adam to have sex, though that was hardly surprising. Most men didn't need convincing. It felt a little strange to listen to his sister's erotic moans as Christian ascended the stairs, but part of him was happy for her. After all, she was striving to get pregnant, and having lots of good sex was the easiest way to make that happen.</p><p>The bedroom was empty, much to Christian's surprise. He hadn't heard Ruby downstairs, either, so he figured she was out on the deck, perhaps in an effort to give Marie and Adam all the privacy they needed, or perhaps because she wasn't all that interested in listening to their moans of pleasure.</p><p>Christian grabbed his wallet and quickly headed out of the bedroom with the intent of quickly letting Ruby know he'd had to come back before leaving for the store once more. He glanced down the hallway to see that Marie and Adam had left the door to their room most of the way open, which struck him as an odd choice, if not a little impolite. After all, why would they think their sister-in-law had any interest in listening?</p><p>Christian was halfway to the stairs when a moan from Marie and Adam's bedroom stopped him in his tracks. It was a moan he recognized. A moan he'd heard countless times before. It was Ruby's moan. But it was a different moan from the first one he'd heard when he walked into the house. He was certain of it, and yet that didn't seem possible.</p><p>He waited in the hallway and listened intently. There was definitely sex unfolding in Marie and Adam's bedroom. He could hear the sound of the bed squeaking a little. He could hear quiet moans. He was confused, though, because there was only one reason he would have heard two women moaning.</p><p>Christian turned towards the bedroom. He tiptoed down the hallway as his heart pounded. He wasn't sure what he was going to see and he wasn't sure he wanted to see it, but he had to solve the mystery that had suddenly presented itself.</p><p>"Oh, fuck, that feels so good," someone said as Christian neared the doorway. It was unquestionably Ruby. He knew his wife's voice. She was having sex. She was fucking Adam.</p><p>"Yeah?" a female voice asked. "Does my husband's cock feel good in your pussy?" It was Marie. It was his sister.</p><p>Christian stopped in his tracks as he seemed unable to propel himself down the hallway. His pulse raced and he felt lightheaded.</p><p>"Yes," Ruby said. "Your husband's cock feels so good in my pussy. It feels so fucking good."</p><p>Christian tried to wrap his mind around what was unquestionably unfolding in the bedroom, but he couldn't quite do it. It seemed impossible. How could his wife, his sister, and his brother-in-law be having a threesome? And if they were, how long had they been involved? How long had Marie known of what Adam and Ruby did when they were together?</p><p>"You look so fucking good riding his cock," Marie said.</p><p>Some of the fog cleared from Christian's head. His sister was watching Adam and Ruby fuck. There was no question about it. Christian couldn't believe it, and yet it was clearly happening. He was just a few feet from the door, too. He could get closer, peak around the corner, and witness the wild pleasures unfolding in that bedroom, pleasures that he'd clearly been left out of.</p><p>"Mmm," Marie said softly. "Your tits look so good, Ruby."</p><p>"You can play with them," Ruby replied.</p><p>Christian's eyes went wide. Was any of this really happening? Was he just having a fever dream?</p><p>"Do it, baby," Adam said. "Play with her tits. Sit on my face and play with her tits."</p><p>Christian heard the bed frame groan. Marie must have joined them. She must have been doing as Adam suggested. Christian stepped closer to the door. He had to. He couldn't help himself.</p><p>"That's it," Ruby said. "Sit on his face. Let him eat your pussy while I ride his big cock."</p><p>Both women moaned as Christian took another step towards the door. All he had to do was turn and look into the bedroom. He was fairly certain he'd see something he never imagined possible when he did, which is why it felt like his heart was pounding so hard it might leap out of his chest.</p><p>Christian took a deep breath, turned, and peered into the bedroom. Adam was on his back. Ruby was naked and riding her brother-in-law's cock. Marie was in a bra and panties and seated on top of Adam's face. Her panties were pulled aside and his tongue was clearly working her pussy. Ruby and Marie were facing each other and Marie was openly groping Ruby's breasts.</p><p>Christian turned away and looked down to see that he'd sprouted an intensely stiff erection. Moans emanated from the bedroom. Moans of pleasure. Moans of intense pleasure. He looked back and saw that Ruby and Marie had leaned towards each other. Ruby had one of her hands in Marie's bra cup. She seemed to be playing with Marie's nipple, and she seemed to be doing a damn good job of it, too, as Marie had a look of utter bliss on her face.</p><p>"I love your husband's big cock," Ruby said. "He makes me feel so good when he fucks me, Marie. He makes me cum so fucking hard!"</p><p>"Cum on his cock," Marie encouraged her. "Be a good little slut and cum all over my husband's big cock."</p><p>Christian was astounded. Completely and utterly astounded. He was turned on, too. Turned on in a way he had never been turned on before. It seemed that his sister, his wife, and his brother-in-law were far kinkier - and sexually open - than he imagined possible.</p><p>Ruby rode Adam's cock harder and faster. Marie took both of Ruby's nipples in her fingers, twisted, and pulled gently. Ruby rolled her head towards the ceiling and Marie leaned in and kissed her neck. Her hands moved down Ruby's back and grasped two handfuls of her ass. Marie then delivered a swift swat, leaving a red mark on Ruby's backside and eliciting a wild moan.</p><p>"Fuck, I'm cumming!" Ruby cried out. "I'm fucking cumming!"</p><p>She came. She came hard, too. Hard and loud. Christian watched in awe as it all unfolded. He played with his cock through his shorts as he watched, too, enjoying the intense sensations of pleasure that emanated through his body with every touch.</p><p>Ruby climbed off of Adam's cock and Marie almost instantly fell into a 69 with him. She took him in her mouth and sucked with wild abandon, swallowing most of his thick, slick shaft over and over while Ruby rolled onto her back and ran her hands over Marie's naked body.</p><p>After an impressive oral display, Marie climbed off her husband's face, straddled his thighs, and played with the head of his cock. "Will you fuck me, baby?" she asked with what sounded like genuine desperation in her voice. "Will you fuck my tight little pussy? Will you fuck me and cum inside me?"</p><p>Adam smiled in the way any man would smile when a woman basically begged for his cock. Then he reached out, grasped one of Ruby's breasts and squeezed it hard as he asked, "What if I'd rather fuck her? What if I'd rather cum in her tight little pussy?"</p><p>To Christian's utter astonishment, his sister moaned. She rolled her head back and reached between her legs to rub her clit while she continued to slowly stroke her husband's cock.</p><p>"Does her pussy make you feel better than mine?" Marie asked.</p><p>It dawned on Christian that his sister might share something very particular in common with him.</p><p>"It does," Adam answered.</p><p>Marie moaned and Christian stared in utter astonishment. It seemed that his sister found the notion of her husband fucking another woman utterly thrilling. "And would you...would you prefer to cum inside her?" she asked.</p><p>Adam sat up and kissed her. "I would," he answered. "But first, I want you to eat her pussy for me."</p><p>Christian couldn't believe what he was hearing. He couldn't believe his wife had kept her kinky involvement with his sister from him. He couldn't believe that Marie was so kinky. He couldn't believe any of it, and yet it was unfolding and his dick was hard as a rock as he witnessed it all.</p><p>Ruby spread her legs and Marie moved between them. She looked up at Adam - who was now lying beside Ruby - and used her tongue as her husband desired. Adam kissed Ruby and played with her breasts while his wife ate pussy on command. Christian watched and stroked his cock through his shorts, bringing himself ever closer to an orgasm.</p><p>"Do you want me to cum inside you?" Adam asked.</p><p>"You know I do," Ruby replied. "You know I love it when you cum inside me."</p><p>Christian knew that was true, and it wasn't long before Marie had moved out from between Ruby's legs to be replaced by Adam. His cock slipped inside her and they fucked missionary style while Marie laid in the bed next to them and masturbated. She played with her tits as her eyes remained focused on the sight of Adam's cock filling his sister-in-law's pussy.</p><p>"Tell me what you want," Adam said to his wife.</p><p>"I want you to cum in her pussy," Marie answered. "Please, Adam, cum inside her."</p><p>Christian remained astounded. He probably could have watched another hour of the threesome and he would have remained astounded. What he'd stumbled on was the most unexpected thrill of his life.</p><p>"Cum inside me," Ruby begged. "Cum inside me while she watches!"</p><p>Adam delivered, and much to Christian's amazement, all three of them came at roughly the same time. Christian came too. He couldn't help it. The whole thing was just too wild and kinky. He came hard in his shorts, making a tremendous mess as he unleashed a far bigger load than expected.</p><p>Adam's cock remained inside Ruby as he kissed her and then looked up at his wife. Marie leaned in and kissed him too, and it looked as though they were all sharing a rather beautiful moment of intimacy, one that Christian couldn't help but feel jealous of as a sense of post-orgasmic delight moved through him.</p><p>Though he was tempted to stay and step into the bedroom to confront his wife, his sister, and his brother-in-law, Christian instead chose to leave. He wasn't the slightest bit angry, and he didn't yet want to reveal that he knew about what they were doing. He was certainly curious to hear all the details - like how long they'd been playing in that way - but that could wait.</p><p>For now, he was going to keep it to himself that he knew and hope that he might get to experience the same sort of thrill once more.</p>