For the Alternate Universes Challenge and the OTP Bootcamp (3. "Don't talk to me") on the BBC Sherlock Fanfiction Challenges forum

In another life, he could have been a consulting detective like he had always wanted be. Had biology played out a bit differently, he could have been out solving crimes.

But the universe hated him. It was the only explanation for his situation. He was forced to hide in the shadows, making sure not too draw too much attention to himself, just in case even one of the humans had enough brains to figure out what he was.

It's for your own good, Mycroft had said.

As if. All his brother cared about was making sure that the humans never found out that the vampires of their mythology were not, well, mythological. If they ever found out that vampires were not only real, but also roamed freely among them, it could be disastrous.

Well, that was according to Mycroft. Sherlock didn't believe it one bit. Mycroft was a bit of a prima donna, the way he liked to exaggerate things. From what Sherlock had seen of humans over his long lifetime, they would be thrilled by the concept of actual vampires.

They had no sense of self-preservation, humans. They'd throw themselves into the closet dangerous situation just because they could.

They were so predictable, so utterly boring.

And Mycroft knew that and still insisted Sherlock needed to find a mate among them.

That was the true curse of being a vampire. It was easy enough for a vampire to walk in sunlight, to pass so convincingly for a human that not even the most imaginative or intuitive person could tell what they were.

But everything had its price, and the price of humanity was dependence.

Each vampire supposedly had a human who was a perfect, for lack of better word, mate for them. They were the ones who would ground the vampire, make their feral traits easier to control, thereby allowing them to pass for humans. They were everything a vampire needed them to be – a companion, someone to feed from, anything.

But then, that was the problem in itself. Each vampire only had one destined mate in his immortal life. Once the mate had been found, it was an easy enough job to make him immortal to match the vampire. But since there was only one mate for a vampire, the vampire had to make sure that his mate was kept satisfied.

An unsatisfied mate could very easily pack up and leave, abandoning his vampire to his feral nature. And so a vampire was dependant on the whims and fancies of his mate, careful of stepping out of line and losing their partner forever.

Sherlock hated the entire concept. Who in their right mind would be willing to bind themselves so completely to another creature, especially if it was a boring human?

But even he grew tired of having five arguments a day on the topic with Mycroft, so here he was, in a human bar, looking for his mate.

At least, that was Mycroft thought. Sherlock was using this outing to freely indulge in one of his favourite pass-times – human watching.

It amused him to end, deducing who and what each person was. Like the man at the bar, who was very obviously married even though he was flirting with every moving female. And the two women near the bathroom. They were second cousins, and obviously madly in love with each other. Not that either of them planned on doing anything about it.

And that handsome man dressed in faded jeans and a soft polo neck – good quality, clinging to his body enough to attract approving attention – chatting up a couple of attractive looking males couldn't be more than twenty-five. No – he had just turned twenty-five, and his friends had brought him here for a celebration. Medical student, graduating soon, and planning to enlist in the army.

For some reason, the thought of that man – whoever he was – getting shot at made Sherlock extremely uncomfortable. The person in front of him was meant to be protected, he couldn't just watch him waltz into-

He let out a barely controlled growl. Mycroft. Of course Mycroft had known his bloody mate would be here today – there was no other reason for him to have suggested this particular bar. The next time he met his brother, he was going to-

"Mate, are you okay?" A voice broke through his annoyed thoughts. A voice as soft as butter, perfect and-

This was why he hated the concept of a mate.

He looked down at the man in front him, fighting down his irritation. If he lost control of his vampire side here, Mycroft would never let him live it down.

"Don't you have some more men to flirt with?" he forced out instead, hating himself for being so harsh with his mate. But this was for the best. "Maybe the next one will take your mind off the reality that your sister is a raging alcoholic." And oh, how Sherlock longed to fix that for him. It wouldn't even be that difficult, really…

Damnit, he hadn't anticipated just how strong the instinct to keep his mate happy was. He would just have to push his body a little further then, to make sure it didn't respond visibly to the man.

"How did you-" The man shook his head, an abrupt movement. "Never mind, that's not why I came over here. I was wondering if you were interested in a dance?"

"Do you always proposition complete strangers?" Sherlock threw back at him. He had to stop himself from getting caught up in him…

"Not at all," the man replied easily, flashing him a quick smile. "Just the gorgeous ones like you. By the way, I forgot to tell you – I'm John Watson. What's your name, then?"

John. Hebrew origin, meaning God is gracious. A strangely ironic name for the mate Sherlock had never wanted.

And yet, his traitorous heart whispered, he isn't put off by my deduction. He's the only person I've met who isn't hurt or insulted by them.

Maybe he truly is my perfect mate.

Sherlock quickly shook himself to clear his head. His thoughts were utterly absurd. The last thing he wanted was to depend on someone.

"My name is Sherlock Holmes," he replied curtly, dismissal obvious in his voice. "And I'm not interested in dancing. Now, if you would kindly find someone else to proposition, I would be most grateful."

"Ah, come on, no need to act like that. It's just one dance."

Obviously, John wasn't about to leave him alone unless he agreed to dance. So Sherlock would accept, and at the end of one song, he'd leave and never see John again.

He would leave London; make sure to stay there until John died. The life of a human was so fleeting to an immortal that he would probably not even notice it.

It was the only way he could think of to make sure he stayed himself.

"Very well," he told the patiently-waiting John. "One dance."

The way John's face lit up in happiness made him want to stay with him, make him happy and keep him content…But Sherlock controlled his body, not the other way around.

At least, that was what he thought. But then they reached the dance floor and John brazenly invaded his space, dancing so close that there was barely any space between them. That, combined with the rhythmic thump of the music blaring from the speakers resulted in some sort of strange hypnotic effect on Sherlock.

All he could focus on was the mesmerizing way John was moving against him, the desperate desire he felt to taste the blood he could see throbbing in the vein on John's neck…it was all he could do not to bite him right there.

Instead, Sherlock settled for burying his face in the little hollow where John's neck met his body, inhaling the delicious scent that was just inherently John, only raising his head to glare at anyone who got too close to his mate.

It was only when John pulled him in for a kiss that he realised that he'd somehow gotten in over his head.

Mycroft was going to be unbearable.

A bit of an explanation of the vampire universe I've created here:

Vampires exist without the knowledge of humans, hiding away from attention for fear of their secret being revealed. They function pretty much like traditional vampires - aversion to sunlight, thirst for blood, high aggressiveness etc etc unless they find their mate.

The "mate" is a regular human who is perfectly matched for the vampire. Basically, he or she will control the vampire's more animal impulses mainly by providing blood, but also by being a partner. Though the arrangement seems to favour the vampire, it's actually designed to protect the human because a vampire is incapable of harming his/her mate. If the mate is unsatisfied/unhappy and chooses to leave, there is little they can do. So each vampire strives to keep their mate happy constantly. If the mate leaves after the vampire has a taste of a life with his/her mate, the vampire tends to go insane and either go on a killing spree or commit suicide.

Because the "mates" are human and mortal, while the vampires are immortal, the vampires have developed a drug that makes the mates immortal without turning them into vampires.

Not all mate-vampire bonds are romantic. Most are, however, due to the simple fact that the two of them are perfectly matched.