I watch as Elizabeth and Paul drive away in their car, waving goodbye until they disappear from view. The beach house is quiet, the only sound is the gentle lapping of the waves against the shore. It's a beautiful night, with a clear sky filled with stars. I take a deep breath of the salty air, savoring the peacefulness of the moment. But then it hits me. We're going to be alone together for three days. I turn to Nate, feeling a sudden surge of anxiety. I know that he's attracted to me, but I've always kept my distance. I don't want to betray my sister, and I don't want to hurt Paul. But now, with no one else around, it's going to be harder to resist. Nate looks at me, his eyes scanning my body. I feel a shiver of excitement and fear run through me. I'm wearing a simple cotton sundress, nothing too revealing, but I can feel the heat rising in my cheeks as his gaze lingers on my breasts. I resist the urge to cross my arms over my chest, instead tucking a strand of hair behind my ear and smiling nervously. "So..." Nate begins, breaking the silence. "What should we do first?" I shrug, feeling suddenly self-conscious. "I don't know... We could watch a movie or something?" Nate nods, and we head inside. The living room is cozy, with overstuffed armchairs and a large couch facing a big-screen TV. Nate flips through the channels, settling on a romantic comedy. I sit down on the couch, trying to relax, but I can feel Nate's eyes on me, and it's making me twitchy. "Are you okay?" Nate asks, sensing my discomfort. I nod, but then I realize that's not enough. "It's just... awkward. You know?" Nate nods. "I know. But we're adults, we can handle it." I sigh. "I know. It's just... I don't want to do anything that would hurt Elizabeth or Paul. Or you, for that matter." Nate leans over and takes my hand. "I know, Susannah. I won't do anything you don't want to do." I feel a sense of relief wash over me, and I squeeze his hand. "Thanks, Nate." We settle back into the movie, but I can feel the tension still lingering in the air. And then, a few minutes later, it hits. A wave of heat floods my body, and I feel my heart rate increase. I look at Nate, and he's looking back at me, his eyes dark with desire. I can feel myself getting wet, and I bite my lip, trying to control the urge to touch myself. "What's happening...?" I ask, my voice trembling. Nate shakes his head, his breathing shallow. "I don't... I don't know." I can see the bulge growing in his pants, and I feel a sudden urge to touch him. I reach out tentatively, rubbing his thigh. He groans, and I can feel him getting harder under my touch. I move my hand up further, feeling his warmth through the fabric of his jeans. I undo his pants and slide them down, revealing his thick cock. I lick my lips, feeling a surge of hunger rush through me. I start stroking him, feeling the smooth skin slide over my fingers. He moans, and I know that he's close. I lower my head and take him in my mouth, sucking hard. He groans again, and I feel him start to pulse in my mouth. I swallow his cum, feeling it slide down my throat. We look at each other, panting and sweating. "What the fuck just happened?" I ask, my voice hoarse. Nate shrugs. "I don't know. But it feels amazing." I nod, feeling the heat still pulsing through my body. "We have to be careful, though. This can't get out of hand." Nate nods, his eyes still hungry. "I know. But... I can't help it. I want you, Susannah." I bite my lip, feeling the tug of desire in my belly. "I want you too, Nate. But we can't do anything that would hurt Elizabeth or Paul." Nate nods again, his eyes dark with hunger. "I know. But can we at least... touch each other?" I hesitate, but then I nod. "Okay. But we have to be careful." We start kissing, our hands exploring each other's bodies. I feel Nate's fingers slip under my panties, sliding over my wetness. I moan, feeling the heat rising higher. He starts rubbing my clit, and I feel my body shaking with pleasure. We collapse onto the couch, his fingers still stroking me, my mouth locked onto his. It feels like time has stopped, like we're the only people in the world. And I can't deny that it feels amazing. It's not until the next morning, when we wake up together, that the reality hits me. We're trapped here together, with no one else around. And we're both infected with the same chemical. Who knows what the next three days will bring? But for now, I'm content to just lay here, wrapped up in Nate's arms, feeling his warmth against my skin. For now, we're safe, and we're together.

The next day starts off innocently enough. We make breakfast together, laughing and joking around like nothing happened the night before. But as the day wears on, it becomes harder and harder to resist the chemical's effect. We're both on edge, our bodies humming with desire. I catch Nate staring at me every chance he gets, and I can feel my own hunger growing stronger. It's like a fever, burning hotter with every passing minute. We go for a walk on the beach, hoping that the fresh air and sunshine will help settle our bodies down. But the moment we start walking, I feel Nate's hand slip into mine, his fingers intertwining with mine. I turn to look at him, and he just smiles. "Let's go for a swim," he says, his eyes shining with mischief. I hesitate, but then I nod. We strip off our clothes and run into the water, splashing around like kids. But our playful antics quickly dissolve into something else entirely. Our hands start exploring each other's bodies, and soon we're locked in a passionate embrace. Nate lifts me up, wrapping my legs around his waist as he pounds into me. I scream his name, feeling the waves crashing against my body. It's like nothing I've ever felt before, a primal urge to mate taking over me completely. And then, it's over. We collapse onto the sand, panting and sweaty. We spend the rest of the day in bed, barely moving except to switch positions. It's like we can't get enough of each other, our bodies addicted to the chemical's effects. I know that I shouldn't be doing this. I know that it's wrong, that it will hurt everyone involved. But in the moment, I can't say no. I need Nate, and he needs me. The next two days blur together, a haze of sex and lust and desire. We barely leave the bed, barely eat or drink or talk. All we can focus on is each other, our bodies entwined in a never-ending cycle of pleasure. But as the third day draws to a close, I start to feel a sense of dread creeping up on me. What will happen when Elizabeth and Paul return? Will they be able to tell what happened between me and Nate? Will our actions destroy their relationship, and maybe even our entire family? I don't know the answer to any of these questions. All I know is that I love Nate, and that I can't resist him. No matter the consequences.