Chapter Text
The call came on an ordinary Thursday evening. If it was anyone else, Sherlock wouldn't have answered.
"John."
"Er, yes. Hello."
"You wouldn't have called if it was something you could say by text."
"Yes, well-"
"Out with it," Sherlock said more forcefully, "I'm terribly busy." He wasn't, his latest case had finished yesterday.
"It's Mary."
Of corse it was.
"There's something I'd like to give her," John explained. "It's very specific and you're the only one I'd trust enough to even consider-"
"I accept," said Sherlock.
"I haven't-" A pause. "You would?"
Sherlock sighed. "To save you the trouble of saying it aloud, I would indeed consent to a threeway with you an your wife."
"How- never mind." Somewhere under John's embarrassment was the hint of a laugh. "This Saturday at nine?"
"If I'm not on a case."
"Fair enough," John said.
They disconnected.
---
There was a new case before the set time, but it was open and shut in less than twenty-four hours. Hardly worth mentioning. The enormous effort Sherlock put into solving it quickly so as to keep his appointment with the Watsons was also of little importance.
Mary took his coat at the door. "Good to see you, Sherlock," she greeted him. Her smile wasn't strained or empty. She was legitimately glad that he was here.
"Mary," he nodded in return. A quick glance over her person told him what would have taken the average person minutes of nervous dancing around the subject to discover. "This isn't a surprise. John told you ahead of time."
Another grin, this one a little cheeky. "That's right."
---
There seemed to be some sort of malfunction in the part of John's brain that was responsible for maintaining eye contact. Everything else was in place, his hand was steady when he handed Sherlock his tea, but he was utterly unable to look at his former flatmate.
Sherlock set the mug in front of him, untouched. Mary sat next to him while John made an excuse to visit the kitchen again. Sherlock watched him leave, weighing the possibility of him backing out of his own offer.
"He'll come around," Mary said.
"Hm," Sherlock mumbled as a response, attention fixed on the kitchen entrance. There was a moment of comfortable silence as Mary finished her tea, followed by a clink when she set her empty cup next the Sherlock's full one on the coffee table.
"Do you mind if I start?" Mary asked.
Sherlock dragged his eyes away from the kitchen and turned toward her. "I see no reason not to."
A slight smile. "Alright."
She straightened up and kissed his cheek. It was light, meant to break the tension. Sherlock could see why John liked her so much. She was as considerate as John was loyal.
Sherlock cupped her face for a real kiss. It was minimal, a simple slide of lips. After a few seconds they separated. Mary got up from the couch and held out a hand for Sherlock to do the same. She didn't let go as she led him to the kitchen. John was fumbling with a coffee maker. It didn't take much to deduce that his guilty look stemmed from the image of the sitting room reflected on the glass of the china cabinet.
"Never mind the coffee, dear," Mary said. "You need some wine, if anything."
"I'm fine," he insisted. Still not looking at Sherlock.
"Come on, then," Mary said, taking his hand. She gently pulled them both to the bedroom.
"Help me with the zipper, John?" she said casually once the door was closed. John visibly relaxed, the hand he placed on her shoulder seemed to be her steadying him more than the other way around.
Mary stepped out of her dress, not nervous at all to be the least dressed in the room. Sherlock found that he wasn't uncomfortable in the slightest as Mary unbuttoned the front of his suit and slid it off his shoulders. His shirt followed in much the same way.
"Your turn, John," Mary said with a playful air. He paced over, stopping wordlessly in front of his wife.
"No, no," Mary chided him. "You've done me and I've done Sherlock. It's only fair the he does you."
John's face flushed, but he didn't move away when Mary tugged Sherlock over to share John's personal space. Sherlock noticed when John's eyes flicked to his face for the barest of seconds, though he said nothing. Sherlock's fingers lifted the hem of his jumper from where it sat on his hips and lifted it over John's head. There was an undershirt instead of a button down underneath. This was John prepared for sex, he supposed.
Sherlock untucked the tighter shirt from John's jeans and pulled that up over his head too. He put an effort into touching John as little as possible, even if it seemed backwards in this context. As a result, John shivered when he did feel Sherlock's fingertips on his skin.
Hands circled around Sherlock's middle and started undoing his fly. A flash of alarm shot through Sherlock's mind before he remembered that it was Mary and not just himself and John in this unusual situation.
"It's okay," said Mary. "Keep going."
Sherlock nodded and continued, dropping the undershirt to the floor. There was an audible gulp from John when Sherlock opened the button of his jeans. Sherlock shifted the jeans off John's hips and let them drop. John was half erect, which Sherlock found surprising with the state of his nerves.
"Pants too, boys," Mary directed. Her tone was gaining authority as the night unfolded. A control kink, perhaps? Or simple impatience?
"Um," John said intelligently. Sherlock froze as well.
Mary looked amused. "That's fine, I'll get them." She got to her knees to be at eye level with the last remaining piece of clothing and glanced up at her husband with another one of those sneaky smiles. John gulped again, apparently knowing the outcome of that particular position.
Mary took hold of the waistband in her teeth and tugged the material down to mid thigh. Her hands brought the pants down the rest of the way for John to step out of them.
"Very good, dear," Mary praised him, placing a kiss on his upper thigh.
Control kink, definitely.
If Sherlock's pants weren't already in pile with his other clothes, he wouldn't have minded the same treatment. What a lucky couple they were, the Watsons.
Before he could process the change, Mary was on her feet again, confident and determined, kissing Sherlock within an inch of his life. It had been some time since anyone had done that, and Sherlock was in such a stupor that it was easy to tip him backwards onto the bed. The rush of arousal was not unwelcome.
"What would you have me do, John?" Mary asked in the pause that she allowed Sherlock to breath.
"Ah." John's voice registered in Sherlock's mind, heated and strained. "Do what you normally do, when it's me."
Mary grinned. "Certainly."
A quick kiss and her flushed face was gone from Sherlock's sight. He propped himself up on his elbows in time to see the lips he had just been snogging wrap around the head of his cock. He gasped and shut his eyes, better to feel her fingers tracing up the length of him, her tongue swirling around the head.
"God, that's hot," John said, vocal at last. "Is that really what it looks like?" He walked to the other side of the bed for a better viewing angle.
"Don't be shy, dear," Mary pulled off, the increased motions of her hand making up for the loss of contact with her mouth. "Play with him a little. The way I like."
The mattress dipped with John's weight. He crawled over, stopping to sit back on his heels beside Sherlock's torso. Sherlock thought he should say something, but Mary's tongue had resumed its work on his cock and he didn't think controlled speech was within his capabilities anymore.
A deep breath from John and words were no longer necessary. He placed his hands flat on Sherlock's chest and dragged them down over his ribs, then the muscles of his stomach. Every inch felt like fire. He wondered through his haze of arousal if he was allowed to kiss and touch John like Mary had to him.
John bent to press a kiss alongside one nipple. His hands continued to massage and stroke the expanse of Sherlock's chest as he got more creative with his tongue.
Sensation was building too quickly. Sherlock knew their evening would be short lived if the focus remained on himself. This was suppose to be about Mary.
"Stop...!" he rasped. Both Watsons looked up at him in slightly comical unison. Sherlock sat up and shifted closer to Mary. He placed his hands on her hips and ran them lightly to her waist and back. "What would you like?"
Mary grinned. "Since you asked- John?"
John reached behind Sherlock for two packages of condoms on the nightstand. He handed one off to his wife.
"Have you done this before?" she asked.
"Not with a woman," he admitted. "but I'm not one to turn down an experiment."
John snorted at that.
Mary grinned and opened the package. She rolled the contents on to Sherlock's length and pushed him onto his back so she could wet his cock with her mouth again. She took the whole of it this time, or close to it; Sherlock was too far gone to know for sure.
To the left of him, John had rolled on his own condom and was applying lube to his now fully-erect cock. If Sherlock hadn't known better he would have thought John was masturbating. A dangerous thought crossed the detective's mind; is this what he would have looked like after dark, alone in his room at 221B? A spike of pleasure that had nothing to do with Mary's tongue shot through him. He wanted to watch John come. He wanted to see him gasping, brow creased with concentration as he brought himself to completion. Sherlock groaned with the new wave of arousal, too late to bite back the sound.
It had been about a minute since Mary had stopped giving him head and Sherlock hadn't noticed, he was so wrapped up in his own thoughts. He sat up and opened his eyes to the most wonderful sight. Mary had moved to be on her hands and knees beside Sherlock; John was smoothing his hands down her thighs and dipping his tongue into her arse. Mary had a content expression on her face and John- Sherlock nearly came right there to see what John looked like doing that.
He was clearly skilled at what he was doing and he... enjoyed it. Sherlock had eaten out a man before and was not fond of the memory. John, however, was almost smiling as he licked and exhaled hot breath on his wife's skin.
Sherlock wanted him. Badly.
No, he chastised himself. This was for Mary. He couldn't be greedy.
Mary sighed happily. "That should do it." She handed the bottle of lube back to her husband. John leaned away from her smooth arse and slicked up his fingers, which he then swirled around her entrance. Sherlock noticed a shiny trail that dribbled down her leg.
It didn't take very long for her to be ready. "Sherlock," Mary said. He tore his eyes from John's movements to give her his attention. "I'm going to be on top of you and John is going to take me from behind. Are you alright with that?"
"Yes," Sherlock said quickly. That meant they would be facing each other. With any luck he would be able to see John's face when he came.
"Good," Mary smiled. She situated herself with a hand on the mattress to either side of Sherlock's head. A look of confirmation from Sherlock and she sank down on his cock. Every inch was hot and slow. Sherlock had never though he could be with a women in this way before. The breasts settling on his chest were uncomfortable and distracting, but he couldn't argue with the arousal that came with the heat and pressure of being inside Mary Watson.
"Hah," Mary exhaled once she was fully seated. "Now you, John." She lifted her hips to accommodate John's height from being on his knees. The sensation the motion caused, the pleasant slide of warm tissue against Sherlock's length, gave a hint of what pleasure was in store once they started moving in earnest. The anticipation was delicious.
"Ah, Mary..." John's voice murmured somewhere out of sight above him. From the give of her hips Sherlock could tell he had sheathed himself in her as well.
"Ready?" Mary whispered. Sherlock nodded and there was a soft grunt of agreement from above. "Alright," she said and began to move.
Her thrusts were shallow at first. Sherlock did his best not to compare the feeling to any of the times he'd been in this position before. He wanted this to be separate and special. Shortly after having the thought he mentally kicked himself for being so sentimental.
When Mary's rocking picked up to the point that she was taking all of him with each motion, Sherlock realized something with startling clarity. He could feel John though Mary's walls. Whereas he had assumed that John was staying still and Mary was doing a majority of the work, he was actually driving downward in time with Mary's efforts. All three of them were pressed tight together at a certain point every few seconds.
Sensations coursed through him too fast to catalogue. He didn't know what to focus on. A lengthy moan from Mary meant she was close. Very close. Her trusts grew erratic and Sherlock felt her natural lubrication drip past his condom onto the skin at the base of his cock. Her fingers wrapped tight in the sheets by his shoulders and her head dropped to pant heavy and wet on his neck. If her head was lower, that meant-
Sherlock's half-lidded eyes snapped open. He was right, John was visible now, and his expression caused a wave of desire within Sherlock that was infinitely greater than he had expected. With every slick snap of his hips John let out a shallow breath and occasionally a raspy moan of pleasure. The open gape of his lips begged to be kissed and Sherlock was all too willing to be the one to do it.
"Ah... Ah, ah!" Mary was coming. Her shoulders tensed and she clenched around Sherlock, laying flat and going still over the whole of his body. She was soundless for a few seconds before her ragged intakes of breath cut the air at Sherlock's left ear. A majority of him felt her tremble though the sensation, but the minority of him that was now free to feel the dull friction of John's cock was what he cared the most about.
He refocused on John. They were so near to each other. John was right there. Right there! If he got up on his elbows he could kiss him. He could kiss that face he had looked across the breakfast table at for years. He could find out what that mouth that produced witty comebacks and beautiful laughter felt like, tasted like. More than anything, he wanted John to look at him and want it too. They were both nearing the end and Sherlock was running out of time to take the chance.
So why didn't he?
Sherlock rose up and pressed into John's mouth with a kiss that was entirely messy, heated, and rushed. John made a small noise of surprise that Sherlock drew down his own throat and answered with a moan of pleasure. He was doing it. He was kissing John Watson. And, oh god, he was coming.
It was the most exquisite orgasm Sherlock ever had. Their mouths were still close but no longer connected. They breathed in each other's air and the slightest touch of their gaping lips only added to the fire Sherlock was feeling. He was light-headed and couldn't think and he loved it. His mind was empty except for the knowledge that John could see him. He had come undone and John was watching every moment if it.
John must have finished just after Sherlock because the three of them were collapsed in a pile when Sherlock came back to a state of rational thought.
"Oh, that was fantastic," Mary sighed. John pulled out and rolled to the side. Mary followed and flopped on top of him. The two began to kiss, sweet and satisfied. Sherlock tried not to feel so cold in the absence of their touch.
He got off the bed and retrieved his clothes. He removed his condom and tied it off before dropping it into the basket beside the married couple's bed. They were still snogging, relaxed and content. Sherlock felt a surge of something unpleasant in his belly. He redressed quickly and had his hand on the doorknob before John's voice stopped him cold.
"Do you really have to leave so soon?"
Sherlock allowed himself a grimace. His back was turned to them anyway. "There's no point in staying."
"Let me at least walk you out," he said. With one last peck on the cheek for his wife, he climbed out of bed and pulled on his trousers, skipping the pants and only remembering to take off his condom when he was doing up his fly.
Sherlock pushed open the door and made his way to the sitting room.
"Thanks for doing this, Sherlock," John said, all honesty, smiles, and post-coital glow. "I know Mary really enjoyed it."
"I'm glad." What else was there to say?
John was avoiding his gaze again. "Would you... be interested in doing this again?"
Sherlock felt guilt, hot and fluid, slosh about in his stomach. He should say no, if not for John then for himself. Nothing good would emerge from a continuation of this arrangement. Especially when he enjoyed it far too much.
Sherlock wrapped his scarf around his neck. "You know where to find me."
I'm sorry, John. I'm not strong enough to say goodbye.