Midnight Fling: My Wife's Sister at the Rooftop Pool

I told myself I wouldn’t go. Sarah had been gone three days on that Denver conference, and the apartment still smelled faintly of her perfume on the pillows. Jenna had been crashing in the guest room for a week while she looked at condos, all sunny smiles and stretchy yoga pants, my wife’s younger stepsister who had always been a little too flirty for comfort. Twenty-six, flexible as hell, that wicked little mouth that said things just this side of inappropriate at family dinners. I’d buried it for years. Married men don’t notice how their wife’s stepsister’s ass looks when she bends to load the dishwasher. Except I did. Every fucking time.

My phone lit up at 11:47 p.m.

Pool’s empty. Come swim. Harmless. Promise. —J

Harmless. Right. I stared at the message long enough for the screen to dim, cock already stirring against my sweatpants like it had been waiting for permission. Sarah trusted me. Sarah was across the country closing some deal. And Jenna was three floors up on the rooftop deck of our building in nothing but whatever scrap of fabric she called a bikini.

I went anyway.

The elevator ride felt endless. Cool night air hit me when the doors opened onto the deserted pool deck—city lights glittering beyond the glass barrier, the water glowing an unreal turquoise under the underwater LEDs. No one else. Just the soft slap of water against tile and Jenna floating on her back in the shallow end like she owned the night.

Jesus Christ.

The string bikini was black, tiny, criminal. Two triangles of fabric that barely covered her nipples, tied with thin cords that disappeared into the valley between her full, firm tits. The bottoms were worse—little more than a V of cloth that vanished between the toned cheeks of her ass when she rolled over and stood. Water sheeted down her body. Yoga had carved her into something lethal: flat stomach with that soft little shadow of definition, hips flared just enough to grip, long legs still beaded with droplets. Her dark hair was slicked back, makeup-free face glowing, lips parted in a slow smile when she spotted me.

“Took you long enough,” she called, voice low and teasing. “I was starting to think you’d chickened out, Mark.”

I walked to the edge like a man approaching a cliff. “It’s late. You shouldn’t be up here alone.”

“I’m not alone now.” She waded closer until the water lapped at the tops of her thighs. Those nipples were hard from the cool air, poking blatantly against the wet triangles. “Sarah would want you to keep me company. Big protective brother-in-law and all.”

Brother-in-law. The word tasted like ash. We both knew the truth of it—the looks that had lingered too long at Christmas, the accidental brush of her hand against my cock that one Thanksgiving when she hugged me goodbye and pressed her whole body in like she was testing something. Years of it, banked heat neither of us had ever lit.

“You’re trouble,” I said, and my voice came out rougher than I meant.

She laughed, soft and knowing, and climbed the submerged steps until she stood dripping in front of me. Up close she smelled like chlorine and coconut sunscreen and pure bad decisions. Water traced the line of her collarbone, slipped between her breasts, soaked into the fabric until it clung transparent. I could see the dark circles of her areolas, the stiff peaks. My mouth went dry.

“Am I?” She tilted her head, eyes dark under the string lights. “Or are you just finally admitting you’ve thought about this?” One finger traced idle circles on her own stomach, just above the waist of those pathetic bottoms. “I’ve seen you looking, Mark. When I do yoga in the living room. When I wear those little shorts to make coffee. You watch.”

My cock was fully hard now, tenting the front of my sweats without shame. I didn’t bother hiding it. The deserted deck, the locked elevator access after eleven, the fact that Sarah was a thousand miles away—it all stacked into something reckless and hungry.

“Looking isn’t the same as touching,” I said, but it sounded weak even to me. “You’re her sister.”

“Stepsister.” She stepped in closer. Wet heat radiated off her skin. “And she’s not here. It’s just us and this big empty pool and whatever dumb promises we make ourselves.” Her gaze dropped deliberately to the outline of my dick. “God, you’re hard already. Does Sarah know how big you get when you’re thinking filthy things about me?”

I should have turned around. Should have gone back downstairs, jerked off in the shower thinking about my wife’s mouth, pretended this never happened. Instead I watched a drop of water slide from her collarbone straight down into the cleft of her tits and disappear.

“This is a bad idea, Jenna.”

“The best ones usually are.” She reached out—slow enough that I could have stopped her—and laid her palm flat against my chest. Her fingers were cool, damp. They slid down, over my abs, and stopped just above the waistband. “I’ve wanted to know what you feel like for years. Every time you and Sarah left the room at family stuff I’d touch myself thinking about your hands. Your mouth. Whether you’d fuck me rough because you felt guilty or slow because you wanted to make it last.”