It really was an accident.

John squeezed his eyes shut against the cacophony that was his flatmate's speech. For 20 minutes now, Sherlock hadn't stopped talking. To himself, to his computer, to the wall of photos and push pins. John had tried to make sense of it at first, had tried to respond to Sherlock's inquiries, but quickly realized that Sherlock wasn't even aware of John's presence. John wondered if this is what it was like inside of Sherlock's head all the time. Was this a verbal realization of his MInd Palace?

And so the noise droned on. Theories, data, wordless sounds tumbled from Sherlock's mouth. John gripped the edges of the book he'd been trying in vain to read. The edges dug into the skin of his palms and John had had enough. He slammed the book shut and stomped his feet to the floor as he stood up and dropped the book onto the footstool. Legs and back straight, he squared himself to where Sherlock sat sprawled on the couch, looking through and past John, nonsense words gathered on his lips.

"Enough!" John said, firmly. "Sherlock, sit up straight and close your mouth."

Sherlock's eyes focused on John's, his face a mess of confusion for a brief moment. John held his breath. In one fluid movement, Sherlock straightened his back, scooted to the edge of the sofa, and planted his feet squarely on the floor, knees and toes pointed towards John. Sherlock's palms flattened against the tops of his thighs and his gaze settled on John's chest at the base of his throat.

Beautiful. John shook his head against the unwanted thought. He drew in a ragged breath. He hadn't thought this through, hadn't considered what he would do with a pliant Sherlock. He hadn't even realized what he was about to do until he'd opened his mouth. He stared at Sherlock with wonderment. His curls stood up on his head where his hands had been tugging them in frustration. His lips were pink and a raw from being chewed. The top lip was sucked just slightly into Sherlock's mouth and John could see his jaw working slightly in an effort to keep from resuming his babbling.

How far would Sherlock let him take this? There had been no conversation. No agreement to terms. No safe word. This was dangerous and stupid and... John's eyes slid over the lines of Sherlock's slim frame, held still and posed for John's approval. He could test it. Sherlock could break scene and John would be okay with that. He wouldn't force Sherlock to continue. He sucked in a ragged breath and steeled his nerves.

"You will remain silent and still for the next five minutes. If you accomplish this, I will allow you to examine your evidence wall. Nod once if you accept these terms."

John held his breath as he waited. His heart thudded against his chest, four long beats before Sherlock's head dipped in agreement.

"Good. Sit just like that, eyes on the table in front of you."

John set a timer on his mobile phone for five minutes and settled back into his chair. He opened his book again and stared at the letters on the page. He couldn't force any of them to form words, let alone sentences, so he merely stared at the mess of black and white until it blurred to gray. He tracked Sherlock from his periphery, expecting movement, expecting Sherlock to crack, to stand up and storm off to his room. John jumped as the timer on his phone sounded. He looked over at Sherlock and was amazed to find him unphased, unbothered by the shrill alarm. He stood before Sherlock again.

"Good," was all he said. Sherlock's only reply was a slow blink and a barely noticeable quick upturn of the corners of his mouth. He silently counted to fifteen before speaking again. "I made you a promise and I intend to keep it. You may examine the wall. However, you will not speak aloud. You won't hum, or whistle, or click your tongue. I expect silence. Nod once if you understand."

Sherlock's agreement came quicker this time, the nod of his head more clearly defined.

"You may begin."

Sherlock waited until John had settled back into his chair before standing and turning to face his wall of papers. He moved calmly, deliberately. Gone was the erratic flailing and impatient bouncing. He stepped onto the couch and stood with his hands at his side, his eyes scanning the documents. His thumbs tapped against the tips of his fingers, the only physical indication that his mind was at work.

He enjoyed the silence and let the peace settle in around him. John watched Sherlock work for several minutes. Sherlock's dressing gown was draped over a lamp across the room and John stared at the muscles of Sherlock's back through the thin material of his tshirt. Silk pyjama bottoms hung from his hips, the fabric shifting along with Sherlock's weight as he balanced himself on the sofa cushions. John was busy studying the slight roundness of Sherlock's arse when Sherlock suddenly exclaimed: "Of course!" John shuddered at the broken silence and stood at once.

"Sherlock!"

Sherlock turned slowly, his head bowed. He stepped carefully from the sofa.

"Do you have anything to say for yourself?" John asked sternly.

A long moment passed before Sherlock replied, "I'm sorry, John, I just -"

"Enough," John cut him off. "I don't want your excuses. I asked you for silence and you failed. You failed me."

Sherlock took a deep breath and curled his shoulders inward.

"Do you want to make it up to me?" John asked and Sherlock immediately nodded and risked a glance at John's face. John gave him a small smile. "Good." At that word, Sherlock's shoulders relaxed. John settled back into his chair and pointed at a spot near his feet. "Kneel here. Palms on your thighs. Back straight. I'm going to read my book and you're going to sit quietly. Nod once if you agree."

Sherlock nodded quickly and made his way to where John still pointed. He settled onto his knees and John retrieved his book once again. He still struggled to find the words on the page, but with Sherlock close enough to notice, he made sure to turn the page every so often. Sherlock's breathing evened out and John watched the rhythmic rise and fall of his back. Before John realized what he was doing, his fingers were tangled in Sherlock's hair. He scratched his nails gently against his scalp and Sherlock shuddered, the steadiness of his breathing disrupted. John tightened his fingers, pulling and lifting upwards. Back arching, Sherlock drew in a deep breath that shook on its way out. He followed that with a breathy noise -not quite a moan- desperate not to break his silence. John loosened his grip, his fingers stroking and soothing.

"In twenty words or less, you may stand and tell me what was so important that would cause you to disobey me."

Sherlock hesitated a moment and John thought that this might be the point where Sherlock breaks. He waits for the explosion, but it never comes. As Sherlock rises to his feet, John realizes with sudden clarity why Sherlock was hesitant to stand. Eye level and an arm's length away is an impressive tent in Sherlock's silk pyjamas. He now knows why Sherlock hasn't stormed off to his room: he's enjoying every moment of this. Really enjoying it. John's own cock gives a twitch in response.

"New rule," John says and licks his lips. It's now or never. How far can he take this? "You still get twenty words, but you also get one stroke," he gestures towards Sherlock's erection, "per word. Only twenty words and twenty strokes. Come before you finish your theory… and I guess we'll never know who done it. I suggest you make them both count. Nod once if you agree to this."

Sherlock stares at him, his jaw slack as he considers John's proposal. Nodding his head, he slides his waistband down his hips and John watches with wide eyes as his erection springs free. Fabric pools at Sherlock's feet and he takes a breath to steady himself. He meets John's eyes before lifting his hand to his mouth. His lips part and he drags his tongue across his palm and then grips the base of his cock. His hand slides up and as he encircles the head of his penis, he says the first word, "Wife-" his hand journeys back to its starting point. Three more strokes reveals "murdered husband, insurance." With another three twists of his wrist he moans, "blue blouse, replaced."

John barely dares to breathe as he watches his flatmate stroke his cock so close to him. He could just lean forward… No. There has to be a line somewhere in all of this. Sucking Sherlock's dick has to be somewhere far, far on the other side of the line.

Sherlock continues, his thumb rubbing against his slit on each upstroke and he tells John, "Tags, receipts. Lover accomplice. Lesbian" Sherlock throws his head back and groans. He shudders through the next sentence, struggling to hold himself together. "Sleeping with husband, secretly."

John is on his knees before he can stop himself, lines be damned. He licks his lips and looks into Sherlock's bewildered eyes. "Four more words," he says gruffly before moving Sherlock's hand aside. Sherlock balls his fists at his side, tremors coursing through his body, as John slides Sherlock's cock into his mouth. He takes as much in as he can before pulling off, leaving the tip between his lips as he looks expectantly at Sherlock.

"Wife," Sherlock squeezes his eyes shut as John repeats the slow slide down and back up. "Murdered," he nearly whispers. "Her," John swirls his tongue around Sherlock's glans, tonguing at the slit.

"One more," he reminds Sherlock before taking his cock all the way in, the head bumping against his soft palate. He relaxes his throat.

Sherlock grips John's by the hair and shouts, "TOO!" as his cock pulses into John's throat. John pulls off and swallows, careful not to dribble onto his shirt. Sherlock falls to his knees, exhausted, and John wraps him in his arms.

"Hey, hey. It's alright," he says as he feels Sherlock begin to shake. "You did good. You did very good."

Sherlock raises his head, his eyes searching. He leans in and presses his lips to John's, tentatively at first. Soon they are both panting into each other's mouths. Sherlock sits back on his heels.

"Thank you, John. I actually… I don't think I could have solved it, if you hadn't pulled me together. I… appreciate it."

John didn't expect this. He assumed that when the high of his orgasm died off, Sherlock would yell. Or throw something. Or storm out. Not this. Sherlock was… thankful?

"I… well… you know… just…" John stammered, unable to make his brain form a cohesive sentence. "You're welcome," he finally managed.

"Platypus," Sherlock stated and began to stand up.

"Platypus?" John asked.

"Yes, for next time," Sherlock replied. "It's awfully irresponsible not to have a safe word."

John stared after him, dumbfounded. Next time.