The moon was high in the sky when Derek's phone rang. He reached for it blindly but upon answering, all he heard was familiar laughter.
"It's two in the morning, Stiles. Come to bed," Derek mumbled, half asleep.
"Derek, I need—ah! I think you—oh!" Whatever Stiles was trying to say was cut off by a low moan.
Suddenly alert, Derek clutched the phone in his fist. "What's wrong? Stiles?"
"Nothing's wrong. But I—" Stiles gasped. "I'm fine. Just get down here."
Despite Stiles' reassurances, Derek threw back the covers, pulled on a pair of shorts and quickly made his way across the property to the greenhouse by the lake.
He'd built the greenhouse as a graduation gift for Stiles, who surprised everyone when he chose to pursue a graduate degree in Botany. Three years later, it was the place Derek could usually find Stiles if he wasn't in the house, even in the middle of the night.
The moon painted the greenhouse with a faint blue-grey hue and Derek sensed a hum of something electric in the atmosphere. He expected to see Stiles bent over his garden table, nose smudged with dirt, talking to his favorite plants or poring over one of the volumes Deaton had given him upon retirement. Instead, Stiles stood in front of a massive plant with thick tentacle-like vines and long leafy stems, gasping and giggling like he was losing an intense tickle fight.
He didn't look like he was in pain but Derek approached him cautiously. "Stiles? What's going on?"
"It worked!" Stiles said, raising his arms in victory. A brilliant smile lit up his face when tiny leaf shoots curled around his wrists. "I did it. I'm doing it. Look!"
"What—" A long tendril twisted around Stiles' forearm, traveling over his elbow and under his sleeve. Derek's mouth dropped open in amazement. "How?"
"I've been working on this for a while but nothing ever happened." Stiles shrugged helplessly. "Then I remembered reading something about the eve of the full moon in one of Deaton's journals, so I came down here to try it out. I just believed I could make it move, and it worked."
"Can I—" Derek stepped closer, reaching out to run a fingertip along the delicate leaves, watching them curl around his knuckle and tickle his palm. Several stems slid around his wrists, tightening their grip and pulling him backwards to where the tangle of vines was much more dense until his bare back made contact with the cool, damp core of the plant.
"Oh!" Stiles shuddered, excitement coloring his cheeks. "I can feel it touching you."
Derek's breath hitched when a thick, green strand wrapped itself around his waist, holding him in place. He pulled against it, surprised by how tightly he was being held, and a rush of heat flooded his body. The familiar scent of their combined arousal hung heavy in the air.
"What does it feel like?"
"Like I have a thousand fingers," Stiles said, pulling his hardening cock from his pants. "Like I'm strong enough to hold you there while they touch you all at once."
Derek gasped as the plant trailed over his shoulders and down his chest, teasing his nipples, sliding down over his stomach. Several stems tickled his toes, then crept up his legs, tracing each curve of muscle.
"Fuck. Please say this is okay."
"Yeah, Stiles," Derek said, breathless. "Whatever you want."
The plant's response was immediate.
Tendrils tangled in Derek's hair, sliding down over his cheeks and lips. They tasted sweet, pure, when Derek opened his mouth to suck on them greedily. Thicker tentacles slipped under Derek's shorts, one coiling around his cock, another sliding back behind his balls, its delicate tip teasing the rim of his ass. It was cool, slick, seeming to draw moisture from its roots to ease the way.
"C'mon. Do it."
The tentacle breached him, filling him up, pulsing in time with Stiles' thrusts into his fist. Derek groaned as the pressure around his cock began to build.
"Gonna make you come," Stiles gasped.
The tip of a leaf dipped into the slit of his cock and Derek surrendered to the push-pull of Stiles' will, letting his restraints hold him up as he shuddered through his release. The tentacle inside him swelled when Stiles came, flooding him with wetness, then slowly slipping out.
"That was incredible," Stiles said, collapsing against his chest.
Derek hummed in agreement, too wrung out to speak.