Author's Note: This is an Omegaverse fic, so if you're not into that kind of thing, I'm sorry you won't be able to enjoy this story, but it's best that you stop reading now. If you're not familiar with the Omegaverse trope, you should probably look it up and decide if it's for you before continuing. To those of you who remain, welcome! I hope you enjoy this story. It's my first in this 'verse (and my first M/M slash, actually), so I hope I tick all the requisite boxes. The plan is for a total of 4 chapters.

Potential trigger warning: As often happens in Omegaverse fic, there will be references to dub/non-con, but none of that actually happens in this story. The fic is rated M for those references as well as language and eventual smut.

This was written for makanivalur in response to her prompt of "Omega!John" for the November johnlockchallenges gift exchange over on Tumblr.

Chapter 1

"Oh, for fuck's sake," snarls John Watson, and heaves himself off his seat at the bar. "I'm leaving."

"What? What did I say?" The man who had been sitting next to him seems genuinely confused. "Come on, luv, you want another pint? Is that it? I'll get you one, no need to take yourself elsewhere, we'll just—"

"No, that is not it, and I'm perfectly capable of asking for a pint when I want one. You—" John stutters, pressing his fingers to the bridge of his nose. "You called me 'honey', and then you licked me."

"So? You're sweet; where's the harm in a man showing you when he's noticed? And don't try to say you didn't want it. Ever since I sat down you've been coming on to me—"

"Answering 'yeah, I saw the match last week' when you asked me does not mean 'please lick my neck, you big stud, I'm gagging for it', I've got news for you," says John. He's shrugging into his coat and digging out the requisite notes from his wallet to cover his tab. The barman raises his eyebrows at him –a Beta, he doesn't want to get caught in the middle of whatever dance these two patrons are performing—but John glowers and slaps the money on the counter so forcefully that the barman opts to appease him instead of the Alpha who is clearly still a bit behind in the uptake.

"Listen, you little tease," the Alpha says as John wipes at his neck with the sleeve of his coat before struggling half-drunkenly with the zip. "You can't just go around presenting yourself like that and then get pissed off when a perfectly red-blooded Alpha responds the way an Alpha should. You bring it on yourself, you do, and you bloody well know it."

John folds his arms in front of his chest. "Oh, do I? And how exactly am I presenting myself? Did I get on my hands and knees and waggle my arse in your face? I don't seem to recall."

"You know what you did." The Alpha is flushed and sputtering now. He waves a hand up and down to indicate that all of John is somehow culpable. "This. You. All –smiling like—and that little—" the hand makes a sideways gesture at the level of John's ribs, presumably at the dark blue cardigan that smartly skims the doctor's trim frame. It is cashmere; John allowed Sherlock to buy it for him after one of his older cardigans disintegrated in an experiment the purpose of which Sherlock shamelessly failed to explain to John's satisfaction. John will never admit it aloud, but the new cardigan has quickly become one of his favorites. He wears it for comfort as much as for the fact that it does actually fit him quite well.

The Alpha's eyes have darkened and his teeth gleam in the dimness of the bar. "You can play innocent and dumb all you want," he says, "but you're old enough to know that if you don't want the attention, you don't come to a bar alone looking so—"

John can see it; can see the word forming in the man's mouth. The hands under his folded arms clench into fists.

"Don't say it," he warns.

The Alpha says it.

"Cute!" John shouts as he sweeps through the doorway to their sitting room.

Sherlock, ensconced in his armchair with his fingers steepled under his nose, looks up from his contemplation. He raises one eyebrow.

"John," he says blandly. "Match over so soon?"

"What? No, it's only" –John looks at his watch—"Sherlock, football matches are –oh, never mind. No, I had to leave, because some Alpha took it into his big thick head that a bit of polite conversation meant I was up for it."

"And just how did he express this obvious misapprehension?"

"He licked me," says John, once again scrubbing at his neck with the sleeve of his coat. Sherlock's other eyebrow joins the first.

"That's hardly polite."

"I didn't think so. Nor was it called for or encouraged in the least; though if you asked him he'd say I was leading him on the whole time. Highly provocative banter involving the relative merits of the opposing teams' midfielders and possible macular degeneration in one or two of the referees. Were you aware that this apparently translates to 'oh please, sir, take me home and impale me on your giant Alpha cock?' Because I hadn't gotten the memo."

"There's no need to be vulgar."

"Yes, there bloody well is, when I can't even have a few pints and watch a match without some great drooling brute sniffing my neck and calling me—"

"—cute," Sherlock finishes for him.

"Oh, not you too."

The detective rolls his eyes. "You were shouting it when you came in. I had wondered what that was about. He did call you 'cute', I presume?"

"He did –among other things." John finally divests himself of his coat and tosses it over one of the kitchen chairs on his way to the kettle. "But it's the 'cute' that really gets up my nose, d'you know what I mean?" He shouts over the noise of the tap as he fetches mugs and tea bags and sets the water on to boil. "I can't get away from it. Bloody Alphas," he fumes, returning to knock his head against the sliding door between kitchen and sitting room. "What exactly is it about me that they all think is so cute? You don't call me cute, or 'honey', or 'sugarplum', or anything revolting like that."

"Good god, I should think not. People actually call you 'sugarplum'?"

"That one's usually female Alphas over the age of, say, fifty. But it's happened."

"John, that is appalling, and unforgivable, and I apologize most sincerely on behalf of my entire gender. I had no idea."

John chuckles. "No need for you to apologize; you're one of the few Alphas I know who are completely innocent of such crimes. I've never thanked you for that, by the way."

"For what?"

"For not treating me the way a typical Alpha treats me. For speaking to me as you would speak to anyone else in your life."

"I don't speak to you the same way I speak to Mycroft, or Anderson, or—"

"Of course not, but how you treat me is based on your impartial assessment of me. John Watson. Not 'unbonded male Omega, late thirties, still got a litter or two in him, pretty good nick despite the shoulder and inexplicably cute.'"

"Ah. Well. You're welcome, though I hardly feel as though I deserve thanks for not being a philistine."

John looks at the genuinely bemused expression on Sherlock's face and laughs for the first time since the big blond Alpha had sat next to him at the bar and flared his nostrils in the direction of John's collarbones.

"Well, if you truly wish to make amends," he says, "Perhaps you can help me stop it happening."

Sherlock frowns. "I don't understand."

"Look, you know all about physical cues, postures, inflections and all that. You study it in suspects and witnesses, use them to impersonate different types of people; you're a master."

"You could study it too, John; it's all on my website."

John waves a hand. "I don't have the patience for that. Besides, why use the website when I can go to the source?" He smiles. "No, I need you to tell me what I'm doing that makes Alphas call me 'cute' and think they can lick me while I'm trying to watch a match."

"You just said you weren't doing anything."

"Not consciously, no; but you'll be able to tell me what I'm doing unconsciously, won't you? There has to be something; this kind of thing has happened to me for years, almost since I presented. That's not just one outfit I wore or aftershave I used, or a single thing I may or may not have said, or even one stupid Alpha who couldn't read a signal if it was written on my forehead in glitter paint. This is a pattern, and I need you to help me break it."

"Why the sudden urgency?"

"Because I'm fucking sick of it! Sherlock, I'm nearly forty. One of these days I might actually like to—" he stutters, unable to explain the flush that he knows has come over him. Sherlock blinks in surprise.

"Mate? Bond? Have children?"

John sighs. "I don't know," he says truthfully, rubbing a hand over his face. "Maybe. Maybe not. I mean, I'm happy enough with the Betas I date—"

"No, you're not."

John opens his mouth to protest, but then gives it up. "Well, maybe if you help me I could attract the type of Beta that would make me happy, all right?"

"No Beta can make you truly happy as a romantic partner, John; it's just biology."

John gapes at him. Sherlock is typing something on his mobile, only half-participating in the conversation.

"Incomprehensible bloody arrogance," says John, fuming. "That, Sherlock? That is why I don't date Alphas. That is why I have Beta sex with Beta women and enjoy perfectly pleasant Beta relationships—"

"—which never work, and which always end amicably because both parties knew it couldn't possibly last, so there's nothing of note to mourn." He rests the phone back on the arm of the chair and looks steadily at his flatmate. "It's not arrogance, John; it's the way your body functions. As an Omega, your reproductive system is constructed in such a way that you experience certain sexual urges only an Alpha can satisfy. You can deny it, keep on trying with your Betas and then whinging when it doesn't amount to anything, but you won't solve your problem that way and I'm pretty sure you know that." He waits for John to respond, but John can do nothing except blink with his mouth hanging open.

"I'm not gloating, John," says Sherlock. "I truly wish that I could tell you differently. I certainly don't know of any Alphas with whom I would choose to bond, if I were so inclined." John huffs a dry, humorless laugh. "Besides," Sherlock continues, "if anyone would champion your cause in fighting biology, it would be me. I would be only too happy to be able to convince my body that it can function entirely without food or sleep—"

"You do, in fact, try to convince it of both those things daily."

"Indeed; and as you have observed my efforts, then you will also observe that they inevitably fail. Because even without annoying ex-army doctor flatmates enforcing the issue, my body knows what it needs and it will break down eventually unless those needs are met –and there is nothing that I can do to change it."

The kettle announces the water's readiness to be turned into tea; John slips back into the kitchen and returns with two mugs, fragrant and steaming. Sherlock takes his from John's hand and inhales.

"Well, ta very much for the words of frustration and doom, Sherlock," resumes John with a wry face, "but that's not actually what I was asking of you. Can you help me or not?"

"What, with the Case of the Unwelcome Adjective? Yes, I think so."

"You don't have anything on right now, do you?"

"Something came up just this evening, while you were out," says Sherlock, "but it's a slow case. Lots of observation and study over time, research –legwork." The two men share a smirk as Sherlock raises his mug to his lips. "I can easily do both at once," he says, and then his mobile rings. He looks at it on the arm of the chair, frowns, and answers it.

"Lestrade," he says. "You have the list?"

Lestrade's voice comes as an electronic mutter against Sherlock's ear.

"No! I told you, she didn't do it! What on earth did you arrest her for?"

More grumbling from Sherlock's phone, a bit louder. The detective heaves a bitter sigh.

"Never mind. You're still at the crime scene? Meet us there." He disconnects with a flourish. "Come along, John. We have Scotland Yard to rescue from themselves."

"So, what's the case?" asks John in the taxi.

"Murder. Male Alpha, 54, stabbed to death in his flat. No sign of forced entry. There was an Omega with him, found at the scene. She was the one who called the police."

"And she's the one they've arrested?"

"Stupid," huffs Sherlock, nostrils flaring in disgust at Scotland Yard's incompetence. John suspects that Sherlock particularly wishes for a cigarette at these moments, to add the drama of twin streams of forcefully expelled smoke to his words. As it is, the detective must dial his voice to Extra Scathing in order to compensate.

John knows he's setting himself up for a Look, but sometimes he can't resist.

"She didn't do it?" he asks innocently.

And there it is. The Holmes "I refuse to dignify that fatuous utterance with a verbal response" Look, number five. Style: Sherlock. (Also available in Mycroft and, presumably, Mummy.) Patent pending. John chuckles to himself as the taxi pulls to a stop outside a modestly posh block of flats and Sherlock sweeps out, leaving John to pay the fare.

Donovan greets him with her usual baffled sneer, as though she is honestly (and unpleasantly) surprised every time she spots him in Sherlock's wake. She shrugs and leads him into the victim's flat, where Sherlock is ordering the medics to unzip the body bag so that his "assistant" can have a look.

The detective and the DI are in the midst of an argument.

"Well, you've arrested the one person besides me who might actually be able to help you in this investigation; I should think you'd be a bit more grateful that I agreed to come by a second time."

"'Agreed' implies I actually asked you here a second time, Sherlock."

"Boys," John interrupts them.

"Hello, John," says Lestrade amiably. "Thought it was your night off."

"Don't even ask."

"John," says Sherlock, dismissing Lestrade with a swish of coat as he turns to the doctor. "What do you notice about the dead man?"

"Um," says John, and approaches the medics who have the corpse on the gurney and ready to roll. "May I?" he asks Lestrade.

"Oh, the more the merrier," gripes Lestrade with a roll of his eyes. The DI's mouth does twitch up at one corner and his glare soften a bit when John gives him a nod of thanks.

"Multiple stab wounds, obviously," says John after examining the body. "Both pre- and post-mortem. Applied with some force, and a bit of rage, I'd say. This is an Omega woman you've arrested?"

"Smaller than you," answers Sherlock pointedly, "26 years old, no military history, works at a café in Soho –and she's unbonded."

"Oh, but then she couldn't have—" John shakes his head. "No, I don't think so. That's what you're saying, isn't it, Sherlock?"

Lestrade shrugs. "The victim was an unbonded Alpha, a bit older than the suspect, obviously, but powerful," he says. "She could very well have taken an interest and let him bring her home, then changed her mind; or maybe he got too forward when she wasn't ready. Panic will give even a relatively weak person unusual strength in a crisis. You both know that."

"Yes, but what you have failed to observe is that these knife-strokes were not made by someone who was panicking. There are no wild misses, no jagged edges; every wound was calculated for maximum effect. Your killer was angry, but not panicked. Also, this Alpha was not unbonded. Or at least, not entirely."

"What? Sherlock, I can smell him all over this flat and I'm a Beta. Surely you—"

Sherlock turns his back again. "John?"

"He's right, Greg," says John. "This man was bonded at one time, but then the bond was broken. Divorced?"

"Widowed," says Sherlock with a grin. "Photos of the two of them in prominent places around the flat. Mantelpiece, over the fire; nightstand by his bed, and so forth and so on. Regularly dusted, regularly handled. He misses her. Obvious."

John rolls his eyes. "I'll take your word for it. The point is, the fact that he's widowed makes it even less likely that your suspect would have panicked enough to do this."

"How's that?"

"Because John is an Omega," snarls Sherlock, "and he knows the difference."

"I'm well aware of John's gender, Sherlock," says Lestrade with a glance at the doctor. Sherlock's eyes narrow at them both. "John," asks Lestrade quietly. "Explain, if you please?"

John sighs. "A man like this –Alpha, powerful, mature, obviously well-off—if he was truly unbonded, as in never bonded at all –well, he'd be extremely attractive to an unbonded Omega who was into that sort of thing, especially if that Omega was looking to bond. But also potentially dangerous. You wouldn't know why they hadn't bonded by that age; they could be incapable of forming those kinds of attachments, or have some repressed tendencies on which they daren't act, or—"

"So what you're saying is that that Alpha could well be a psychopath," interjects a smirking Donovan. "In other words, a freak."

"Or they could just be completely uninterested," says John sharply. Donovan stiffens, but Sherlock sees her blink twice and take a slightly deeper breath as she meets John's eyes and takes in the firm set of his jaw.

"Anyway," continues John, "as attractive as such an Alpha might be, he'd still make even me a bit nervous –at least, until I got to know him better." Another glare at the sergeant. "And especially at certain points in my heat cycle. If it was time for one of my heats, I wouldn't volunteer to be alone with this guy unless I knew I wouldn't mind if he decided to jump me. Or unless I was prepared to face assault charges when I defended myself," he adds with an artless smile that both Donovan and Lestrade return without thinking.

"But if he had been bonded once, even if the bond had been broken, you wouldn't feel that sense of danger in his presence, would you?" Sherlock prompts him.

"Mm? Oh, no, not at all," answers John. "No, the fact that he had bonded in the past means that he was both willing and capable; the fact that he was widowed means that the bond was severed without his consent. He wasn't without a bondmate on purpose. It makes a big difference."

"You would have felt safe to be alone with him."

"Well, as a rule, yes. I mean, there are always exceptions. Just as not all truly unbonded Alphas of a certain age are necessarily psychopaths" –Sherlock pretends not to notice John's sharp sidelong glance at Donovan, but Lestrade ducks his head and chuckles silently behind his hand— "neither should all widowed Alphas be dismissed as harmless. But it would take a real act of aggression to work your suspect up to doing this. Were there any wounds or marks on her when you found her?"

"None," says Sherlock with a smile for his assistant.

"And they hadn't known each other long, had they?"

"Not long enough for either of them to build up the kind of resentment that would have prompted a deliberate attack of this degree of ruthlessness."

"Then I'm sorry, Greg, but Sherlock's right. You shouldn't have arrested her. I can't see how she could have done it."

Lestrade puts a hand to his eyes and rubs at the closed lids. "Be that as it may," he says wearily, "she's all we've got and we're holding her until we can get some answers. She's guilty of obstructing a police officer at the very least. Won't give her name or address, has no ID on her, and refuses to say anything except she was with the victim and another bloke, the two men got into an argument, she hid in the bathroom when the argument got physical, and when all was quiet and she came out again, our Alpha was like this." He nods at the corpse.

John frowns. "She won't say who the other bloke was? Or describe him at all –tall, short, old, young, Alpha, Beta or Omega?"

"Nope."

"Hmm…" John licks his bottom lip thoughtfully, and then looks up at his colleague. "Sherlock?"

Sherlock waves a dismissive hand. "Yes, she's clearly hiding something but you won't get it out of her. At least," he scowls at Lestrade, "not before I solve this murder my own way, if you would stop thinking, do as I ask and get me that list."

The DI remains unflappable. "You'll have your list tomorrow," he says, "and much good may it do you. In the meantime, we can hold Miss Anonymous on the obstruction charge for up to a month. But if my nose is right," he adds wryly, "she'll go into heat before then, and she won't want to be in prison for that. Good evening, gentlemen." He gives a nod each to John and then Sherlock and strides from the flat.

"'List'?" asks John on the way back to Baker Street.

"The victim was the owner of a small but moderately prosperous commercial laundry and linen service," Sherlock explains. "The list I asked Lestrade to provide is a list of new clients that the service has acquired over the past three months."

"Okay," says John after trying to work out the connection for a moment. "Why?"

Sherlock gives a short, impatient sigh. "Think, John," he says. "You said it yourself: those stab wounds were vicious and deliberate. Someone hated that man –or at least wanted him dead, and not on the spur of the moment. But you also noted that he seemed a stable, safe, boring sort of man."

"Hang on a minute, I never—"

"—and you were right, by the way," continues Sherlock as though John hadn't spoken. "Good god, the man hadn't changed so much as a single picture in his flat since before his mate died. No new –whatevers, Omegafriends, Betafriends, renters, anything. No new hobbies, no bad habits, no unfortunate life choices even in the mourning period. He was on a heart-healthy diet. Took a moderate walk every day and a single glass of red wine in the evening while relaxing with a light comedy or one of those 'action' films in which nobody bleeds. Everything about him for years has been just like this. Safe. Stable. Dull."

"That, Sherlock, is what most people would call 'normal' for someone of his age."

Sherlock looks at John across the back seat of the taxi and smirks. "I heard those inverted commas, John, and I hope that you have come to terms with living outside of what most people would consider 'normal'."

"I come to terms with it every day, Mr. Holmes." If John's grin is any indication, he doesn't much mind. "So –the business, then? The new contracts?"

"Ah, yes; the laundry and linen service was the only part of that man's life that had undergone any significant change in years. That must be the key, the reason for someone to want to kill him now, as opposed to any other time."

"I hadn't realized that commercial laundry services was such a cut-throat industry."

Sherlock allows himself a slight grimace at the pun, but soldiers on. "Not –usually, no; but it's a more lucrative business than you might be aware of. Think of all the hotels in London, all the restaurants, convention centers, gyms, spas, salons: any business that requires bed linens, towels, table linens, uniforms—"

"I get it. It's a lot of laundry."

"Potentially, yes. And there were a few larger, well-known firms that handled most of it for the bigger clients, and still do; but, the recent downturn in the economy has forced some of those establishments to cut corners."

"Including, possibly, hiring a smaller and less expensive company to service their laundry needs."

"That's the hypothesis."

"You really think one of the bigger companies sent someone to kill this man because he'd siphoned a hotel or two off their client roster?"

"In terms of raw cash, won and lost –well, people have killed for less. But as a business measure, it is a little unorthodox, not to mention carrying a high degree of risk for what seems a doubtful reward. So what was special about this man, or about these particular clients?"

"I guess it depends on who those clients are," says John, and takes a sharp breath. "Oh, so that's why –yes, I see. The list," he says, as Sherlock heaves a sigh of infinite patience at last rewarded. He doesn't look at John –his eyes are watching London slide by outside the taxi's windows—but that private, pleased smile of his is visible all the same.

"Knew you'd get there eventually."