Warnings: Mild violence, sexual content, and a fleeting reference to drug use, including bartering sex for drugs; see the prompt for further details.
Spoilers: Minor for The Great Game
Disclaimer: Arthur Conan Doyle is the original creator of these characters; this story is based on the 2010 Moffat/Gatiss/BBC update. I make no claim to the characters or series, and no copyright or other infringement is intended.
Summary: Witnessing Sherlock kiss another man prompts John to make a move. The results aren't necessarily what he expected.
A/N: For Tattoo Kink's LiveJournal's sherlockbbc community's Make-Me-a-Monday request for BAMF!possessive!John (inlcuding marking-biting-claiming) and proudly!Sherlock who wears/shows his marks (to Lestrade/Mycroft/anyone). The story includes all the elements of the prompt but took a couple of unplanned turns on the way. My thanks and gratitude to Evilchuckles for Brit-picking and Sunspot67 for the beta review.

Possessive, Possessed

"How far would you have let him go?" John asked as Sherlock flagged down a taxi.

"It didn't come to that, so it's pointless to speculate." John shot him a look to see if the innuendo was intentional, but of course it wasn't. Sherlock believed that brazen directness was the best way to proceed from point A to point B, as if everything in life could be reduced to a geometric proof.

They had tailed the man to a bar. (John thinks his name is Ken, but he isn't sure since he's only heard it once.) John sat in the corner nursing a pint while Sherlock slid into a seat at the bar and began chatting Ken up. John felt pangs of regret when he had to turn down offers of drinks from more than one bloke; under other circumstances, he would have accepted, but he needed to stay clearheaded while he kept an eye on what was going on. Keeping the idiot genius out of harm's way was itself a full-time job.

Forty minutes afterward, John's phone beeped.

Find a hiding spot in the alleyway.
SH

Why?

Surely even your brain isn't that tiny.
SH

While searching for the alleyway Sherlock had directed him to, John wondered how his friend had managed to text without attracting Ken's notice. He took in the stench of beer, grease, and urine as he hid behind a skip filled to overflowing with boxes and other debris. Wedging himself between the chilly metal bin and the uneven surface of the next building made his bad shoulder ache more than it had in months. Running his fingers across the wall behind him confirmed his assumption that it was made of stone. It was good to know that he'd started picking up Sherlock's observational skills; it was one benefit of sharing a flat with the often-infuriating man.

He wrapped his arms around his chest; earlier, he hadn't wanted to carry a jacket, but now he wished he had another layer between him and the suddenly chilly mid-September air. He peered out when he heard footsteps rounding the corner. Only the moon and a solitary streetlamp illuminated the scene, but that was enough by which to view Sherlock's distinctive silhouette enveloping the shorter and huskier Ken. He wondered if Sherlock's open-necked shirt and snug-fitting suit were enough to keep him warm, even taking into account the heat that contact between his body and Ken's provided.

Even though John knew Sherlock was playing a part, his gut churned at the sight of their embrace. He slid his fingers over the gun stuck in his waistband for reassurance and told himself that he had to stay calm. He was only here to observe and get them out safely if things turned nasty. Surely Sherlock was as uncomfortable about this as John was; he didn't normally let anyone get this close.

His heart jolted as he watched Ken pin Sherlock against the tavern wall. Ken lifted his chin and Sherlock ducked his head so their lips could meet. John couldn't see well enough to make out the details, but he could hear obscene smacking noises and imagine the exchange of tongues and saliva that caused them. He willed himself to unclench his muscles and relax; the smallest movement or noise might give him away.

He looked up again when Sherlock slammed Ken against the building. Ken yipped "Ow!" and panted as Sherlock shoved him even more forcefully. John winced. He was glad that they were no longer kissing and Sherlock was in control of the situation, but he wasn't convinced this level of brutality was necessary or helpful. He'd rather they get out of there quickly.

"What are you doing?" Ken shouted. "You wanted it! You aren't one of those crazies who goes around beating up men who make a pass at them, are you?"

Sherlock hissed, "Tell me what I want to know, and you can leave with your dignity intact. Refuse, and my friend will take a picture of us that I'm sure your boyfriend would be interested in."

John shook his head over this fresh piece of near-blackmail. He was thankful that Lestrade didn't inquire into Sherlock's interrogation methods. They didn't rise (or stoop) to the level of some Allied interrogators he'd known in Afghanistan, but they wouldn't hold up under close scrutiny, either.

"You're bluffing. You have no idea how to find Godfr-" Ken stopped, aghast at how much information he had already given away.

Even though he couldn't see it, John knew that Sherlock's lips were curled up in a sneer. "Please. Match your puny wits against mine. Make my day."

Ken gave way and gave up the name they wanted in an unintelligible stream of words that Sherlock had to have him repeat, much to his consternation. When he was finished, Sherlock pushed him towards the street while taunting him with "There, was that so hard?" For his part, Ken took off like a shot.

Sherlock strode toward the other end of the alley, John running after him. Sherlock muttered to himself that it made no sense to say "Make my day" when it was clearly nighttime.

John marveled that Sherlock had remembered the infamous catchphrase from Dirty Harry and consoled himself that this proved that his program of cultural re-education had not been a complete waste despite Sherlock's repeated threats to delete it all from his hard drive.

They didn't talk on the way home. John was still alittle winded from running to keep up with Sherlock's longer stride. Sherlock drummed his gloved fingers restlessly on his thigh. John wanted to grab his hand and force him to stop the pointless motion, but he knew it was futile, and possibly counterproductive, to thwart Sherlock's attempts to work off his excess energy.

John himself was far from calm inside. He could feel the clamor of his heartbeat, the blood pumping through his veins, and the adrenaline in his system sending his peripheral nervous system into overdrive. None of this made any sense; the encounter was over, and Ken hadn't chased them or posed any kind of a threat. John's presence hadn't even been necessary, as things turned out. All he'd been was an unwillingbut necessary voyeur.

John reflected that either Sherlock was an exceptionally gifted actor or his disavowal of any interest in sex when they'd first met had been a load of bollocks. Not that it mattered to John one way or the other – he'd been telling the truth when he'd said it was all fine with him – but he'd wanted Sherlock to level with him so he'd know what to expect. That was before he'd learned that Sherlock was even more friendless and adrift than he was.

He thought of the heated kiss he'd just witnessed and Ken pinning Sherlock against the wall. Sherlock had lush, sensual lips, lips many women would kill to have – but since when did he notice, let alone think about, his flatmate's lips? It must have been seeing them pressed against another man's that had sent John's mind careening down such a dangerous path.

When John looked down, he discovered that he'd balled his hands into fists. He forced them open, but not before Sherlock noticed and quirked an eyebrow at him. This was Sherlock's first acknowledgment of his presence since they'd gotten into the taxi. John huffed and shrugged his right shoulder. His left was still sore from being pressed against the stone façade.

Sherlock slid out of the taxi with typical grace when it pulled up to their doorstep, leaving John behind to pay the fare. It was just as well that Sherlock gave John free rein with his debit card; otherwise, John would have felt that he shouldered more than his fair share of their living expenses. Extravagant taxi rides were only a part of it.

John just barely managed to grab the front door before it clicked shut in his face and forced him to fish his key out of his pocket to unlock it. "Christ, Sherlock, can't you wait long enough to make sure I'm actually on the steps before you let go of the door?" he sputtered.

Sherlock shrugged, and John suddenly had enough. He pushed Sherlock up against the stretch of wall between the front door and the stairs, grabbed the back of Sherlock's neck, and pulled him down for a kiss. Angling their faces so their noses wouldn't collide, John pushed his slightly chapped lips against Sherlock's moist ones and began nipping at Sherlock's lower lip. By the time Sherlock's lips parted, John had drawn blood; the faint coppery taste of it lingered as he explored Sherlock's mouth.

Sherlock didn't resist, though he tensed up. John let go and thought he was unresponsive as well as unresisting until he noticed Sherlock's head tipped back, exposing his neck and chin. His face was lax and his breathing labored, his mouth open and gulping for air.

Taking up the implied invitation, he started sucking on Sherlock's collarbone. He moved from one side to the other, licking, nipping and pulling at the skin tautly stretched over solid bone. He bit down at the junction of Sherlock's neck and shoulder before peppering wet kisses and suck marks up the side of his neck.

He wanted Sherlock. Desperately. Wanted to brand him, claim him, inscribe the message "John Watson was here." He took a gasping breath and fused their mouths together, sucking hard against Sherlock's lips and tasting the fading tang of blood.

John broke the kiss and leaned his forehead against Sherlock's. "Come on," he rasped as he pushed Sherlock up the stairs.

Sherlock paused when they reached the first floor landing. John urged him upward. Wrestling on the sofa would only make his shoulder worse, and using Sherlock's bed? God, no.

He felt Sherlock shiver and wondered if he was having second thoughts, though his shallow breathing and glazed over eyes suggested otherwise. "Are you okay with this?" John asked without explaining what "this" was. He wasn't sure himself. "Whatever is fine with you is fine by me."

Sherlock gave him an unreadable look before starting up the stairs to John's room. John let out a small sigh of relief and followed, clutching at whatever of Sherlock's he could hold onto without stumbling.

Sherlock stopped at the threshold. "Sherlock, please. I need – I want – this. You," John said in a broken voice and angled for another kiss. Sherlock leaned forward and tugged John closer. Feeling Sherlock's erection pressing against him made John's throb in response.

Sherlock broke away and John followed him into the room. John ran his hands down Sherlock's arms before pushing the jacket off his shoulders. "Impatient, aren't you?" Sherlock said with a smirk, catching and draping the garment on John's dresser.

John pushed Sherlock onto the bed, heedless of the clothing separating their bodies. Sherlock groaned when John leaned over and pressed his hand down on Sherlock's groin. John scrabbled on top and rocked against Sherlock's hip; Sherlock curled his fingers around John's arse, pulling him in closer.

Just as he settled into a rhythm intended to get them both off soon, John's last remaining shred of rationality absorbed the rustle of fine wool against denim. He stuttered to a halt.

Sherlock lifted his head and said, "Problem?"

John sighed. "Let's get our clothes off first, okay?" He hoped that Sherlock didn't need him to explain why they should strip before going any further.

He was relieved when Sherlock shed and flung his clothes on the floor without any comment or argument. John did the same while wondering if Sherlock's cavalier treatment of his usually immaculate clothing was a sign of how far gone he was. Clothes shed, they resumed rocking and rubbing against each other, John teasing and sucking on Sherlock's nipples. As they got closer, he dug his fingers into Sherlock's hips (mine) and raked his nails down Sherlock's back (no one else's). By the time he wrapped his hand around both their erections, he had in his frenzy left five more bruises, a host of scratches, and a love bite in addition to the ones already in full, multicolored bloom.

Two tugs, and John felt the bliss of orgasm wash over him. John wrung a corresponding orgasm out of Sherlock after recovering from his own. He then rained careful kisses on all the marks he could find, from the bruise on Sherlock's left hip to the scratch on his abdomen upwards to the suck marks on his chest and continuing until he reached the bites on Sherlock's collarbone and the bruises on his neck. Sherlock's hand combed through John's hair throughout this exploration, and when John reached his chin, he pulled John closer for another kiss.

John rolled off and dragged the duvet out from underneath them. He raised the covers so Sherlock could crawl in beside him, all the while expecting him to beg off and potter around downstairs the rest of the night as he usually did.

To his surprise, Sherlock slid in beside him and clicked off the bedside lamp. "Go to sleep," he said before curling up next to John, his knees touching the side of John's leg. John lay on his back staring at the stains on the ceiling that he couldn't see in the darkness until he turned away and fell into an exhausted sleep.

John woke up the next morning groggy and disoriented. His dreams had consisted of flashes of him and Sherlock rutting together needily interspersed with the images that had pervaded his nightmares since his return: body parts raining down like shrapnel and young men he couldn't save dying in agony in the field. He rubbed his eyes and remembered that the images of Sherlock letting John bruise and bite him were not a figment of his imagination.

He reached over to pat the other side of the bed. Sherlock was gone and the sheets were lukewarm. Sherlock hadn't left hours ago, but he hadn't just gotten up, either.

He whipped his head around, panicked at not having the ability to gauge Sherlock's mood right away. He'd crossed a line last night - a line he hadn't intended to cross, ever. (At least possibly ever.) It wasn't as though John had never considered it, but every time he did, he decided that he didn't want to muddle their friendship and mostly peaceful coexistence by introducing sex into the mix. Now he'd run roughshod over that barrier with possessive fervour.

He felt a bit punchy as the events of the prior night filtered through his mind. His minimal alcohol consumption couldn't possibly explain his disorientation. Maybe it was the result of finally getting off with someone for the first time since he'd been invalided home. Damn it all, just thinking about it was making him hard again.

Had that really been him shoving Sherlock up against the wall and marking and molesting him before making him come? Where did he get off acting like a jealous boyfriend? They'd never even kissed before. For all he knew, last night had been the first time Sherlock had experienced orgasm at someone else's hand. Or it could have been the hundredth time; John had some uneasy suspicions about how Sherlock had paid for the drug habit he claimed he'd given up.

He'd let what he'd witnessed goad him into ignoring Sherlock's warning that he wasn't interested in him. He'd instigated it all, and although he'd asked Sherlock if it was okay, he hadn't spelled out what that meant – mostly because he hadn't known either until they were in the midst of it. Those were just excuses, though. Once they were lying naked together, what the hell did he think was going to happen?

He started when he heard the door creak. "Your scruples are tedious and beside the point," Sherlock said.

John didn't want to look at the flatmate he'd seduced last night, but he needed to find out how upset he was and why. When he opened his eyes, he saw Sherlock leaning against the door, arms crossed and with a frown on his face. He was fully dressed, but John could see bruises and teeth marks on his neck and collarbone.

"I didn't mean to do that. I'm sorry."

Sherlock's frown deepened. "Keep your cheap apology. I know you meant what you did. You know it too. Lie to yourself if you must, but don't lie to me."

"I'm not lying," John said heatedly as he sat up, sheets bunched up over his lap so his nakedness wasn't totally exposed. "I swear to God I didn't mean to cause that much damage."

"Appealing to a non-existent deity doesn't add any weight to your statement. What makes you think you've caused any damage? This is nothing compared to other injuries we've sustained, or have you forgotten that?"

Leave it to Sherlock to bring up what they'd gone through since the incident at the pool. John shuddered. "No, I haven't forgotten," he said quietly, "but those things were done by criminals we were chasing, not by one of us to the other."

Sherlock made a dismissive sound and clasped John's face between his hands. "Don't be idiotic, John. I'm far from shy about my opinions. If I'd wanted you to stop, I would have told you so."

"Sometimes people let things get away from them in the heat of the moment." As soon as he said it, John realized that it was a stupid thing to say.

Sherlock snorted. "You think that an impending orgasm overcame my better judgment? Really, John."

"All right, I get your point. Now leave so I can shower and dress in peace."

"Don't take long. Lestrade texted to ask if I wanted to observe the interrogation of the man whose name Ken gave me."

John rubbed his head. "He's not going to let you interrogate him yourself, is he?"

"No. But he's willing to let me watch and see what I pick up about the man and whether he's telling the truth." Sherlock turned around and left as abruptly as he'd entered.

John had hoped that Sherlock would button his bloody shirt the rest of the way before they left. He knew it might cause remarks or raised eyebrows, as Sherlock habitually left the top couple of buttons undone, but he hoped they'd chalk it up to a run-in with a suspect rather than a run-in with him.

But as usual, Sherlock didn't behave with any sense of discretion or self-protection. Why had John thought – even hoped - that he would? Instead of covering up like a normal human being, he'd flared his shirt collar out more than usual to better expose the marks.

Dimmock started and stared when they passed his desk. Donovan intercepted them before they reached Lestrade's office. "The DI's down the hall," she said, her attention on the sheaf of papers clutched in her hand rather than them.

When she looked up, her eyes widened and her mouth formed a startled O. She darted a puzzled glance at John as he shifted uncomfortably, then stared at the area just below Sherlock's chin again. Her thoughts could not have been more obvious.

"Can you take us to Lestrade now?" Sherlock asked. Donovan rolled her eyes and nodded. "Is my neck truly that fascinating? Surely it's not something you haven't seen before."

John wanted to sink through the floor to ground level, call a taxi, and slink away. Donovan refused to look either of them in the eye as she stomped down the hallway, jostling people walking in the opposite direction.

She led them to a side hallway with a one-way mirror overlooking a dingy windowless room with a table and four scuffed chairs. Lestrade sat with his back to them; a stocky man with wavy ash blond hair sat on the other side facing them.

Sherlock watched intently. When his shirt cuff rode up, it exposed a bruise on his right wrist. Donovan tugged on John's hand and led him to an alcove in front of the restrooms. "Have you lost your mind?" she said as she whirled around to face him.

John was really not prepared to discuss this today. "Apparently," he said wearily, calculating that remaining silent would only encourage her to talk more.

"I hope you know what you're doing. He's dangerous, and I don't want you to be the one on the mortuary slab someday."

John shrugged as she walked away. Although he didn't share her conviction that Sherlock would literally be the death of him (though they both knew it was not at all out of the question for him to meet his death helping Sherlock catch criminals), he was in no shape to convince her that he knew what he was doing when he wasn't sure himself.

When they returned, Sherlock behaved as if he hadn't noticed that they'd been gone. After wrapping up the interview, Lestrade sent Donovan away to get someone to escort the suspect to the detention cells.

"We've got him dead to rights," Lestrade told Sherlock as John looked on. "A search of his flat turned up stolen jewelry – necklaces, watches, you name it." He examined Sherlock curiously. "You weren't attacked, were you?"

"If by 'attacked' you mean 'criminally assaulted,' then no," Sherlock said disdainfully.

John once again wished he were elsewhere. Lestrade glanced at him silently for a moment, then cleared his throat and said, "Right, then." Mercifully, he didn't mention it again.

As Sherlock and John walked out through reception and onto the street, they had the good fortune to stumble across Anderson, who was holding a cup of coffee in one hand and a pastry in the other. Sherlock almost ran him over when Anderson cut in front of them on his way into the building.

"Look where you're going, you prat," Anderson said, catching his coffee cup before it landed on the pavement. When he looked up and saw who it was, he said, "Oh, it's you," with remarkable venom. "I should have known."

"As should I," Sherlock said smoothly. "I do believe you were not paying attention, but it doesn't surprise me in the least that you have no motor control."

Anderson stared at Sherlock's neck, apparently transfixed. "What happened –"

Sherlock ran a finger underneath his shirt collar and walked around Anderson without waiting for John to follow. He stuck his arm up to hail a taxi. John nodded at the dumbfounded forensic analyst and darted toward the curb as Sherlock got in. Sherlock would probably have left him standing there if he hadn't caught up first.

After the taxi sped away, John noticed Sherlock's mouth curl up into a self-satisfied smirk. "Did you maneuver me into that?" he asked. When his question was met with a silence and a knowing glance, he huffed, "You mad bastard!" and settled back into his seat, arms crossed. He was royally screwed. Sherlock would never let him forget or live it down. The only consolation was that maybe, in all this, he was going to get to screw Sherlock in return. Willingly.

Now there was a thought.