How did I let myself get talked into this?

Dippers eyes darted around as he followed Mabel down the darkened corridors of the building, brushing the too-thick layers of dangling cobwebs away from his face.

"You know, when you used to tell me that you'd had a fantasy about us having sex in a haunted house I'd always thought that you were joking," he whispered to her.

Mabel's hand squeezed Dippers fingers slightly, feeling the nervous sweat on his palm against her skin and she grinned to herself.

"I probably was, but I thought that we shouldn't waste this opportunity since it came up," she whispered back.

Halloween had come and gone, and since the last trick or treaters were long since tucked into bed the haunted house had been locked and bolted shut by the owners and the volunteer monsters had all gone home. In another day the haunted house would return to being an old warehouse and all of its plastic and rubber horrors would be packed away in storage boxes until the next year came around again. Of course there weren't many locks that could stand up to the combination of a bent paperclip and Mabel's determination, and it hadn't taken much coaxing to bring Dipper along with her.

The two turned a corner and found themselves in a large chamber. A backdrop of a huge moon rising over a graveyard dominated the far wall, its craters painted in a way that gave it a very skull-like appearance. The twins flashlight beams swept the room, casting crazy shadows off the foam tombstones jumbled across the floor in crooked rows. Mabel's beam reached the corner of the room and she gave an excited gasp.

"A fog machine! Oh this is perfect - do you think it still has any juice?" she asked Dipper as she pulled him toward the device.

"I'm not sure this is really a good idea," Dipper said.

"Oh come on, we're already breaking and entering here its not like they can charge us with unlicensed use of the fog machine or anything like that," Mabel scoffed as she knelt down and started to fiddle with the machines controls.

"Well, yeah… I don't know, I was hoping we could talk our way out of it if anyone showed up," Dipper said.

"What, like we got lost on our way home and ended up in a locked haunted house at 1 AM?" Mabel said.

"Yeah, I guess that one does sound pretty weak," Dipper admitted.

He swept the beam of his flashlight around the room once more.

"Maybe we could tell them that we came in to pay our respects to our dear departed friend," he paused the beam on one of the tombstones and squinted as he read the name aloud, "Seymour Butts,"

A whirring hum cut through the oppressive silence of the empty warehouse and Dipper jerked in surprise before he saw Mabel standing up from beside the now active fog machine and dusting off her hands theatrically.

"Nothing like a little fog to add to the romantic ambiance," Mabel said, rolling the 'r' of romantic like a gumball on her tongue.

"Well, when I think romance I think misty fake graveyard," Dipper answered with a nod.

"Well, maybe you didn't before but you might soon," Mabel said in a teasing tone as she walked over to Dipper and slipped her arms around his neck to pull his mouth to hers.

Nervous as he was, Dipper couldn't help but respond to the heat in Mabel's kiss and his own arms moved out to pull her to him, palms sliding along her back and sides. She was still wearing the main part of her Halloween costume from earlier that night, a flimsy black dress with small spider-web lace accents and a spider-web edged skirt so short that it left her shapely legs bare to mid-thigh.

I really should have suspected that she was up to something tonight when she decided not to go with one of her usual goofy costumes this Halloween, Dipper thought to himself.

Those thoughts quickly fled from Dippers mind when he felt Mabel's hands start to fumble with the catch of his belt, her sharp teeth nipping at his ear in a way that sent a shudder down his spine. His own hands slid down her back and made their way up under her skirt, kneading the firm flesh in his fingers in a way that he knew she loved. A breathy moan floated up from the darkness and he felt an appreciative bite latch onto his neck, Mabel's cupid-bow lips sucking gently on the skin.

Dippers flashlight dropped from his hand and rolled across the floor, and he felt rather than saw as Mabel moved against him in the darkness, dropping low. She made a small noise of triumph as she succeeded in working his belt open in the complete darkness surrounding them, her hands stroking up along the inside of his thigh with care before she zeroed in on her goal.

Dipper stifled a gasp as he felt Mabel's breath, warm in the cool air against his skin, and he had to lean back up against the wall as she took him in her mouth. His hands slipped down to stroke against her hair. Every sensation felt more intense in the dark and it wasn't long before Dipper had to push gently against Mabel's shoulders to move her away and catch his breath.

"So, what do you think of my idea now?" Mabel said as she rose up, her grin evident in her voice.

Dipper responded by pulling her close for a deep kiss. His nightvision had finally started to make sense of the weak illumination provided by their discarded flashlights, and he slid his hand down the gentle curve of her stomach and under the waistband of her skirt. Mabel hissed softly as his fingers stroked up against the soaking wet skin in teasing circles, pressing down with just enough pressure to make her dig her fingernails into his shoulders.

Mabel shoved Dipper back and turned around, hiking the edge of her skirt up over her hips and swaying her bare backside gently to a rhythm only she could hear.

"Are you going to keep me waiting or what bro beau?" Mabel asked, her voice shaking with anticipation.

Mabel's breath caught in her throat when she felt Dippers hands grip her waist tightly, and her knees buckled slightly when she felt him graze up between her legs, accidentally brushing up against her clit with a misaimed thrust. She made a small frustrated noise in her throat and reached down between her legs to help guide him in and this time when he moved she had to lean up against the wall to keep her balance. Her breath escaped her in a shudder, her eyes closed tight as she reveled in the feel of fullness that always came when he was inside her like this.

They moved awkwardly in the darkness, working to keep their balance but not letting up for a second. Mabel slipped a hand down between her legs, stroking herself in furious counter-rhythm to Dippers thrusts as she felt herself getting closer to the edge and she gasped out frantic encouragement whenever she felt him start to slow. Sweat slicked Dippers forehead and he felt his heart hammering hard enough to burst in his chest, but just when he thought he would have to stop for breath he felt Mabel tighten around him in a spasm, a high whine hissing out from her clenched teeth and her fingernails scrabbling against the wall. Dipper couldn't hold himself back at that point and he pulled Mabel tight up against him as he shuddered to a stop, his breath coming out in ragged gasps.

The two sought each others lips in the dark, sharing a salt-slick kiss as they leaned together for support against the wall.

"So," Mabel panted as she pulled her skirt back down over her hips, "I have this idea for Christmas…,"

Dipper shook his head and shakily bent down to pull his pants back up over his waist.

"Well, I'm definitely listening," he said.

"Ok, now hear me out: you know those little Santa's Villages they put up in the mall?" Mabel asked.

"You can't be serious," Dipper said in a flat tone.

"Can't I?" Mabel asked sweetly.

"God I love you," Dipper said as a giddy laugh bubbled up from his throat at the thought.

"Love you too Dip," Mabel replied, giving in to the giggles as the pair stumbled together on shaking legs out of the room, hand in hand.