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The Science of Jealousy

Summary:

Only an hour ago, Sherlock had been grasping at any excuse to convince John to head straight home. He’d called the idea of a pub gathering ‘an offensive waste of cognitive resources.’ Now, however, as he felt the weight of Watson’s burning gaze following his every move, his perspective was shifting.
DI Miller’s hand landed at the small of his back. John was at their side within four seconds.

or

Sherlock was quietly testing the limits – how far he could push John before he snapped, hauled him back to Baker Street, and showed him precisely what kind of consequences came with provoking a former soldier.

Notes:

This idea has been stuck in my head for a while now, so I finally decided to turn it into a fanfiction. A bit of jealous John and teasing Sherlock.
Enjoy!

Chapter Text

Tonight, they finally managed to close a case that had dragged on for months. Dubbed “The Weaver” by the press – a nickname Sherlock thoroughly despised – the investigation had gripped London in a state of paralysis. For four months, the city had been terrorized by a series of abductions that defied all logic. The perpetrator left no DNA, never appeared on CCTV, and seemed to possess an almost impossible knowledge of the city’s hidden “blind spots.”

The complexity lay in the geographic inconsistency. Victims disappeared from locked rooms in Chelsea and reappeared days later, unharmed but mentally shattered, in derelict warehouses in East End. There was no pattern to the victims – no shared age, gender, or profession – only a strange, intricate silk thread left in their pockets, knotted in patterns that resembled ancient navigational charts. Sherlock had spent weeks on the floor of Baker Street, surrounded by maps and thread, his mind whirring so fast he’d forgotten to eat or sleep. 

The breakthrough finally came when he realized it wasn’t a criminal organization or a ghost; it was a logistics expert for the London Underground. The killer had been using the forgotten tunnels – sections of the Tube closed since the Blitz – to move throughout the city unseen. He wasn’t just kidnapping people; he was “mapping” them, treating the citizens of London like variables in a grand, twisted experiment on urban movement.

The final confrontation happened in the depths of the abandoned Down Street station. In the pitch black, guided only by the distant hum of the Jubilee line, Sherlock and John had chased the Weaver through a labyrinth of rusted tracks. It ended with John making a near-impossible shot through a steam pipe to pin the suspect down without killing him – saving Sherlock, who had been seconds away from being pushed into the path of an oncoming night train.

Upon their return to Scotland Yard, Greg all but dragged the entire team to a nearby pub to celebrate the victory. The moment Sherlock heard the suggestion, he pivoted on his heel – but before he could take a single step toward the exit, John caught him by the elbow.

“You’re coming too,” John said firmly, when Sherlock looked up at him with something dangerously close to a kicked-puppy expression.

“I don’t see the point, John,” Sherlock hissed. “We’ve caught the man. The data is filed. Why must we stand in a room full of shouting people and mediocre ale?”

“Because it’s called socializing, Sherlock,” John replied. “Try it. For me.”

Sherlock frowned. He could try many different things for John. But socializing? Extremely dull, almost painfully boring, and – quite frankly – a hazardous waste of a high-functioning intellect. He finished the thought in his head, though the look John gave him suggested he might have muttered it aloud anyway.


The pub was hot, smoky, and deafening. The air was a thick slurry of spilled beer, salt-heavy chips, and the heat of too many bodies. Scotland Yard had claimed the back corner, their laughter and shouting ricocheting off the low, nicotine-stained ceiling. Space was at a premium, but after several rounds of cheap lager, the concept of personal space had ceased to exist.

Sherlock sat wedged tightly between John and Lestrade. Watson’s thigh pressed firmly against the detective’s side, a solid, grounding weight. Almost absentmindedly, John’s fingers began to trace slow, rhythmic circles against the smooth fabric of Sherlock’s trousers. Sherlock leaned into it, a quiet thrill running through him; he had always lived in his head, but he found he thrived when John touched him with such effortless, casual intimacy. The sensation of John’s thumb moving against the fabric was a distraction Sherlock hadn’t accounted for. It was a silent conversation happening beneath the table, completely ignored by the boisterous crowd of detectives surrounding them.

“So, Sherlock,” a masculine voice cut through the haze.

The detective lifted his head toward the source of the sound. Sitting opposite him was DI Miller – the Yard’s so-called “Rising Star,” who practically preened in the glow of Sherlock’s presence. Miller was everything Sherlock usually despised in a detective: he was earnest, he used modern police jargon like “synergy” and “proactive engagement,” and he was currently leaning so far into Sherlock’s personal space that he was nearly sniffing his scarf.

“The way you narrowed down the Down Street entrance,” Miller continued, his eyes wide with a sort of frantic, puppy-like adoration. “It wasn’t just logic. It was... instinct. I’ve read your blog, obviously, but seeing it in person? It’s something else entirely. It’s like you’re tuned into a frequency the rest of us can’t even hear.”

The hand on Sherlock’s thigh tightened. The rhythmic circles stopped, replaced by a firm, heavy pressure. John didn’t look up from his drink, but Sherlock could feel the shift in his breathing – shorter, shallower, the quiet preparation of a man ready to move.

The corner of Sherlock’s mouth twitched. Interesting.

John was not, by nature, a jealous man – or so Sherlock had concluded after observing him through the entirety of his past relationships. He hadn’t minded when his girlfriends went out drinking with friends, when they had male colleagues, when they texted someone else during dinner. He didn’t make scenes, didn’t check their phones. Sherlock had always had the distinct impression that it simply hadn’t mattered to him all that much.

But when it came to Sherlock, the rules of engagement had shifted entirely.

Sherlock considered this as he felt the heavy, territorial weight of John’s hand. It was a fascinating deviation in John’s psychological profile. With those women – Sarah, Jeanette, Mary – John had been the picture of relaxed trust, perhaps because he had never truly feared losing them, or perhaps because the stakes had never been high enough.

With Sherlock, however, there was an edge. It wasn’t about control; it was about possession. John didn’t check Sherlock’s phone because he knew Sherlock found most other intellects faintly offensive. But place a man like Miller in the room – someone who looked at Sherlock with a mixture of professional hunger and personal awe – and the soldier in John Watson rose unmistakably to the surface.

“I don’t have ‘instincts’, Inspector,” Sherlock replied, his voice a cool, sharp contrast to the humid warmth of the pub. “I have data. If the rest of the Yard chose to stop blinking for more than five seconds at a time, they might find themselves on my ‘frequency’ as well.”

Miller laughed, a bit too loudly, and leaned even closer. The scent of his expensive, citrusy aftershave clashed violently with the pub’s earthy aroma. His hand now rested on the table, directly across from Sherlock’s pint. From the corner of his eye, the detective noticed John glaring at it every time it shifted a millimeter closer. If looks could kill, Lestrade would already be drowning in paperwork.

“Always so modest,” Miller said, his voice dropping into a register that was far too intimate for a public house. “But look, I’ve been going over the Weaver’s knot patterns. I think there’s a direct correlation with the 2009 ‘River Walk’ cases. I’ve actually developed a digital mapping system based on your blog’s principles of spatial analysis.”

Sherlock tilted his head, a deliberate, slow movement that brought his face closer to Miller’s. “Digital mapping? Most of your colleagues at the Yard can barely operate the kettle, Miller. You’re suggesting you’ve built a predictive algorithm?”

“I have,” Miller said, his eyes bright with the thrill of Sherlock’s undivided attention. He moved his hand again – a bold, sweeping gesture that ended with his fingers resting mere millimeters from Sherlock’s own. “I’ve got the preliminary data on my tablet. I was thinking... since you’re the architect of the logic, maybe you could take a look?”

Before Sherlock could respond – or before John’s hand tightened with enough force to leave bruises on Holmes’s thigh – Lestrade pushed back his chair and stood.

“Next round’s on me,” he announced, his voice booming over the pub’s din.. “After this case, damn it, every single one of you’s earned it more than anyone else.”

A chorus of whistles and applause broke out. The sudden movement at the table acted like a bucket of cold water; Miller snatched his hand back from the table as if he’d been burned, his face flushing a deep, embarrassed red.

“Miller. Anderson. With me,” Lestrade said briskly, nodding toward the bar.. “You can help me carry the beers.”

As Miller reluctantly pushed himself away from the table, casting one long, lingering look back at the detective, Sherlock felt a sudden, searing heat against his ear.

“I was starting to worry that if you spoke to him one more time, he’d wet his trousers,” John murmured, soft and dangerously low against his skin. “I’m surprised he hasn’t started telling everyone at the bar yet that he’s just had a conversation with the Sherlock Holmes.”

John was so close that his lips brushed the sensitive skin at Sherlock’s temple, the stubble of his jaw ghosting over the detective’s cheek. The casual intimacy was gone, replaced by a focused, heavy intent.

Sherlock’s breath hitched, a small smirk playing on his lips as he stole a glance toward the bar. He shifted just enough – a fraction of an inch – so that their lips were nearly touching. The scent of John – tea, old wool, and that sharp, metallic edge of adrenaline – filled his senses, far more intoxicating than any alcohol in the room.

“How do you know? Maybe that’s exactly what he’s doing right now,” Sherlock joked, his voice a low vibration. He didn’t pull away. He didn’t blink. He kept his gaze locked onto the dark, swirling depths of John’s eyes, watching the way the pupils swallowed the blue iris.

“Let him,” John whispered, his hand on Sherlock’s thigh tightening again, no longer tracing circles but grounding him there, claiming him in the middle of a room full of people. “Let him talk all he wants. But he’s not the one going home with you.”

The challenge was clear. Sherlock felt a thrill run down his spine that had nothing to do with the case they had just closed. He had spent months hunting a killer in the dark, but the most dangerous thing in London was currently sitting six inches away from him, smelling of lager and looking at him like he was the only person in the world.

“No,” Sherlock agreed, his voice barely a breath. “He isn’t.”

Their private bubble was abruptly burst by the heavy thud of glasses hitting the wood. Lestrade distributed the pints with a grin, before raising his own high above the chaos.

“To finally catching that son of a bitch!” Greg shouted, his voice thick with relief.

A chorus of cheers echoed him as everyone slammed their glasses together, indifferent to the beer sloshing over the rims and onto the sticky table. Sherlock went through the motions, his hand steady as he raised his glass, but his mind remained sharply focused on the periphery. He didn’t need to look directly to feel it: Miller was staring.

Even as the DI laughed at something Anderson said, his eyes kept darting back to Sherlock, filled with that same frantic, hungry light. He was watching the way Sherlock sat, the way he held his glass, and – most dangerously – the way he was still leaned almost entirely into John’s space.

Sherlock took a slow sip, his eyes tracking Miller over the rim of the pint. He felt John stiffen beside him. The brief, playful softness from a moment ago vanished, replaced by a cold, tactical stillness. John had noticed the staring, too.

John reached for his pint and took several long, deep swallows. When he finally set the glass back down on the worn wood, it was already half empty. This time, Sherlock didn’t even bother to hide his smirk.

John Always-Stoic Watson was truly, undeniably jealous.

It was a fascinating development. Sherlock hadn’t seen him in this state for a long time – not since the early, adrenaline-fueled days of their partnership, and certainly never with this level of raw, territorial intensity. The detective found himself cataloging every symptom of John’s “affliction”: the rhythmic tapping of his foot, the heightened skin temperature, the way his pupils remained dilated even in the harsh, flickering light of the pub.

Miller, meanwhile, seemed to interpret Sherlock’s smirk as a sign of encouragement. He leaned forward again, trying to bridge the gap John had created with his arm. 

“So, Sherlock,” Miller began, raising his voice to compete with the toast erupting nearby. “About that mapping system. I really think—”

At that exact moment, Watson lifted his hand and placed it against the exposed skin just above the collar of Sherlock’s shirt, his thumb grazing the nape of his neck. It was a bold, unmistakably public claim – one that sent a shiver down Sherlock’s spine that had absolutely nothing to do with the cold draft from the pub door.

Miller froze mid-sentence, his mouth slightly open, as his gaze dropped to John’s hand. 

Sherlock, for his part, went remarkably still. The touch was electric. John’s thumb moved in a slow, possessive arc against his skin, a sensation so grounding it threatened to shut down his cognitive functions. He could feel the heat of John’s palm, the calloused texture of his skin, and the sheer, unyielding weight of the claim.

“You were saying, Inspector?” Sherlock prompted, his voice coming out a fraction thinner than he intended.

Miller cleared his throat, his eyes darting between Sherlock’s pale face and John’s grim, steady stare. Sherlock was almost certain the Inspector had received the message and would finally understand that he wasn’t a prize to be won. Instead, the man simply took another sip of his beer and continued as if he hadn’t noticed the hand clamped firmly onto the back of Sherlock’s neck at all.

Oh, so Detective Inspector Miller had no intention of backing down so easily. Brave. Or perhaps just incredibly stupid.

“The thing is,” Miller said, his voice regaining its polished, professional sheen, “the data doesn’t lie. I’ve been looking at your pathing during the Down Street chase, Sherlock. You moved with a logic that even the GPS couldn’t predict. I’ve integrated that into the Vector. If we could just sit down with a terminal – even for twenty minutes – I think we could solve the 2009 cases by morning."

Sherlock felt the hand on his neck tighten. John’s thumb, which had been grazing his nape, was now pressed hard against the base of his skull. It was no longer a caress; it was a physical restraint.

“Twenty minutes,” Sherlock repeated, his voice dangerously smooth. He was watching the way John’s knuckles had turned a ghostly white on his pint. The experiment was reaching its critical mass. “In a ‘focused’ environment, as you suggested? Just the two of us and your laptop?”

“Exactly,” Miller said, leaning in even further, emboldened by Sherlock’s tone. He was ignoring John so pointedly now that it was practically an insult.

Sherlock truly began to fear that if even one more word fell from Miller’s lips, John would lose the microscopic scraps of patience he had left. The air between them was humming, a live wire stretched to the breaking point. Sherlock could feel the tremors in John’s thigh, the suppressed military precision of his anger just waiting for a target.

But before the explosion could occur, a heavy hand suddenly dropped onto Sherlock’s shoulder – and it didn’t come from the side where Watson was sitting.

“Hey, Sherlock, John,” Lestrade chirped, turning toward them with the flushed, happy glow of a man three pints deep. “I was just telling Sally about the way you—” He suddenly froze, his sentence dying in his throat as he finally registered the atmosphere.

Lestrade’s eyes darted between John’s murderous, flat stare and Miller’s indignant expression. The young Inspector looked like a man who had been seconds away from a conquest, only to be blocked by his superior officer for the third time that night. The silence at the table was sudden and deafening.

“I… hope I didn’t interrupt something?” Greg asked, his voice dropping an octave as his internal policeman’s intuition finally screamed that he was standing in the middle of a minefield.

John’s gaze shifted to Lestrade, and the change was instantaneous. The feral, protective edge softened – just enough to be civil. Greg was a friend, a comrade-in-arms, and therefore exempt from the carnage John was currently contemplating for Miller. John took another long, slow pull of his beer, his eyes never leaving Lestrade’s as he gave a short, jerky nod, encouraging the older man to keep talking.


Sherlock stood with his hip leaned casually against a bar stool. The alcohol was a pleasant, low-frequency hum in his veins, warming him from the inside out and softening the usual sharp edges of his mind. John stood right beside him – so close that Sherlock could feel the radiant heat of the doctor’s body through the layers of their clothes.

Sherlock has been watching the room like a cat watches birds, cataloguing every drunken confession, every lie told to a spouse on a mobile, every flicker of attraction. DI Miller has been orbiting for twenty-three minutes. DI Miller was making his third pass. He was using the tactical "approaching-the-bar" maneuver, but his trajectory was far too calculated to be a simple thirst for lager.

Sherlock watched him in the reflection of the mirror behind the bar. Miller’s pupils were dilated – not from the dim light, but from the adrenaline of a man about to take a gamble. He was smoothing his tie, checking his reflection, preparing to insert himself into a space that was already occupied.

John’s voice cut through the hum, silk over steel. “If he doesn’t stop looking at you like that in the next thirty seconds, I’m going to do something deeply unprofessional.”

Sherlock’s mouth curved, sharp and delighted. This was better than the case. This was better than the chase. “Such as?”

“Such as dragging you out of this pub by the back of your coat and reminding you – in considerable detail – who you belong to.” John’s lips brushed the sensitive skin just behind Sherlock’s ear as he spoke. “And I won’t be subtle about it.”

A shiver raced down Sherlock’s spine, bright and electric. He tilted his head, offering more of his neck without conscious thought, a silent provocation. “You realise Lestrade would never let you live it down.”

“Lestrade can sod off,” John said, his voice dropping into a rougher, darker register. “He’s already half-drunk and trying to get Anderson to do karaoke. He won’t notice a bloody thing until tomorrow morning when he sees the bruises I’m about to leave on your hips.”

Sherlock’s pupils flared – dark, hungry. He turned his face fully toward John, their noses almost touching. The rest of the pub, the Yard, Miller, the clinking glasses – it all receded until there was only the heat of John’s breath and the iron grip anchoring him.

“You’re being territorial,” Sherlock observed, voice pleased.

“I’m being accurate,” John countered.

Sherlock laughed softly, a low vibration that seemed to settle right in his marrow. He wouldn’t admit it out loud, but God, he loved this side of John. The raw, unyielding edge of the soldier, the man who stopped being a “blogger” or a “doctor” and became something primal, something that only Sherlock seemed capable of evoking.

“I’m getting us another round. Don’t move,” John muttered, his hand lingering on Sherlock’s shoulder for a fraction of second longer than necessary before he turned toward the bar.

Sherlock watched him go, feeling the sudden absence of John’s heat like a physical chill. He leaned back against the bar stool, his eyes half-lidded, still savoring the taste of the adrenaline John had just stirred up.

He didn’t have to wait long. Within ten seconds, the air on his left shifted. Miller didn’t just stand nearby this time; he moved into John’s vacant space, leaning his elbow on the bar so he was angled directly into Sherlock’s personal bubble. He smelled of scotch and overconfidence.

“I don’t think we’re destined to talk in peace today. You know,” Miller started, his voice dropping into a smooth, conspiratorial hum, “this place is... loud. Crass. And the lager is mediocre at best.” He leaned in closer, his eyes fixed on Sherlock’s mouth. “I have a bottle of 18-year-old Macallan at my place. We could actually run the ‘River Walk’ algorithm properly. No distractions. No... background noise.”

He cast a quick, dismissive glance toward the bar, where John was waiting for the pints. John had gone perfectly still. He was standing with his back to the bar, both hands gripping the edge of the wood, watching the exchange. He wasn’t moving. He wasn’t interrupting. He was just watching, his eyes like blue flint.

Sherlock felt a thrill of pure electricity. He knew John was reaching his limit, and the fact that John was staying back – waiting to see what Sherlock would do – was more intoxicating than the alcohol.

“A different location?” Sherlock mused, tilting his head. He didn’t pull away as Miller leaned even closer. “And better alcohol. You’re quite determined, Inspector.”

“I know what I want when I see it,” Miller said, his voice thickening. He took a bold step forward, his knee brushing against Sherlock’s thigh. He reached out, his hand hovering just inches from Sherlock’s waist.

“My partner is quite… territorial,” Sherlock murmured quietly, observing Miller’s every move with the detached fascination of a scientist watching a moth fly into a blowtorch.

“I don’t see a ring. And I don’t see him right now. Let the doctor finish his beer. He’s a big boy; he can find his own way home. Come with me. Let’s see what that ‘frequency’ of yours can really do when you’re with someone who can keep up."

Miller’s hand finally landed. He gripped Sherlock’s hip, his fingers digging into the fabric of his shirt. It was a firm, possessive pull, an attempt to claim space that didn’t belong to him.

At the bar, John’s knuckles turned a ghostly, bloodless white against the dark wood.

“You’re very brave, Miller,” Sherlock whispered, his eyes darting to John. “Or very, very stupid.”

“I’m neither,” Miller laughed, feeling the victory. “I’m just—”

The air in the room didn’t just shift; it vanished.

John didn’t shout. He didn’t run. He moved with a terrifying, silent efficiency that belonged on a battlefield. One second John was at the bar; the next, he was there. He didn’t hit Miller. He did something much worse. He stepped between them, his body a solid, immovable wall of muscle, and grabbed Miller’s wrist – the one on Sherlock’s hip – with a grip that made the Inspector’s bones audibly creak.

“Sherlock and I were just leaving,” John said firmly, a sharp, tight smile on his face that didn’t even come close to reaching his eyes. It was the smile of a man who was counting the seconds until he could be violent.

Miller’s breath hitched, his eyes widening as he tried to pull his wrist back, but John’s hand was an iron shackle. The doctor’s presence was overwhelming, a cold, focused fury that made the “Rising Star” look like a flickering candle in a hurricane.

When he finally managed to wrench his arm free, Miller cleared his throat weakly, his bravado replaced by a frantic need to salvage what was left of his dignity.

“Uh, right. Next time, then,” he stammered, his voice thin and cracking.

John was seconds away from tearing him apart in the middle of the pub. He took a single step forward, closing the gap until Miller was forced to lean back against the sticky bar top.

“There won’t be a next time,” John said politely, though the words sounded like gravel under a boot. “If I see you even so much as look in his direction again, I assure you, we won’t be having such a pleasant discussion.”

The silence that followed was absolute. Miller didn’t wait for a third warning; he turned and vanished into the crowd, his tail between his legs.

John didn’t watch him go. He turned his head slowly toward Sherlock. The “stoic” doctor was gone, replaced entirely by the soldier who had just defended his territory. His pupils were blown wide, and his breathing was heavy, ragged with the adrenaline of a fight he hadn’t quite gotten to finish.

Without a word, John reached out and snatched Sherlock’s coat from the hook with a violent, snapping motion. He didn’t just hand it over; he shoved the heavy wool against Sherlock’s chest, closing the distance between them so abruptly that their foreheads nearly collided.

“You,” John hissed, his breath hot and smelling faintly of the lager he’d barely finished. He was so close that Sherlock could see the pulse thrumming in his neck. “Taxi. Now.”

The command was raw, stripped of its usual polite veneer. Sherlock felt a jolt of pure, unadulterated triumph. He let his fingers curl into the fabric of the coat, but his eyes remained locked on John’s, absorbing the heat of his anger. He didn’t move fast enough to satisfy John, so the doctor reached out, his hand finding the nape of Sherlock’s neck once more, not to caress this time, but to steer him firmly toward the exit.

They cut through the pub like a blade. Lestrade started to say something – probably a parting joke about the “Mapping Inspector” – but he took one look at John’s face and thought better of it, raising his glass in a silent, wary salute instead.

The cold night air hit them like a physical blow as they stepped onto the pavement, but it did nothing to dampen the fire between them. John didn’t let go of Sherlock’s arm. He stood on the curb, his frame tense, scanning the street for a yellow light with the lethal focus of a sniper.

“John,” Sherlock started, his voice a low, vibrating hum, “the Macallan—”

“If you finish that sentence,” John interrupted, his voice dropping an octave as he finally spotted a cab and raised a sharp, commanding hand, “I am going to forget that we are in public, Sherlock. I mean it. Get in the car.

A black cab screeched to a halt beside them. John yanked the door open and practically bundled Sherlock inside before sliding in after him and slamming the door shut with a finality that echoed down the empty street.

As the taxi pulled away, the dim, orange glow of the streetlights began to flicker across their faces in rhythmic intervals. The silence in the back of the cab was heavy, charged with everything that hadn’t been said – and everything John was clearly planning to do.

Sherlock shifted, leaning just slightly closer, as if testing the limits of the space between them.

“Don’t just be angry, John,” he said lightly. “It’s tedious. If you’re so bothered by the fact that he touched me…” His mouth curved in a sharp, deliberate smile. “Then reclaim the space. Mark the territory.”

He pulled back just enough to meet John’s gaze, his expression devastatingly smug, openly challenging.

“And when we get home,” Sherlock added softly, “make it hurt. I want to feel every bit of that territorial streak you’re so proud of.”

The sound that tore out of John’s throat was something between a snarl and a choked breath of frustration. He lunged across the seat in one brutal motion, his hand flying to the back of Sherlock’s neck, fingers tangling hard in the curls there as he yanked his head back.

“You think this is a game,” John hissed, his face inches away, eyes blown wide with a frightening, feral intensity. “You think you can play with me like one of your bloody experiments.”

He didn’t kiss him.

He held him – immovable, unforgiving – knuckles white, thumb pressing hard at the hinge of Sherlock’s jaw.

“You want it to hurt?” John’s voice dropped to a register that made the hair along Sherlock’s arms rise. “Be careful what you wish for. Because by the time I’m done with you tonight, you won’t be able to stand – let alone smile.”