Author's Note: Within twenty-four hours, last week's fic skyrocketed to being the most popular of this series yet. I'm interested to know what about it made it so special. Thanks so much to everyone who left a review or a favourite!

A million thanks to my beautiful beta, Becca (Ao3's LlamaWithAPen).


Prompt from Tumblr user shittemore's "some neighbour AUs" post: It's like 3AM and my roommate locked me out of the house and I forgot my keys and I'm really drunk pls take pity on me and let me crash at your place for the night o' neighbor of mine AU.

Drunk

Friendship comes in many forms.

Sometimes, friendship comes in football games or study groups, learning from each other, challenging each other to do better without realising there was ever any real competition.

Sometimes, friendship comes in emails, sent whenever you have the chance, to someone you never see in person but feel close to nonetheless.

Sometimes, friendship comes in hugs, or squeezes on the shoulder, and reminders that you are never alone.

And sometimes, friendship comes with pounding on the door at three o'clock in the morning, slurring, "BILL IF YOU DON'T LET ME IN RIGHT THIS INSTANT I'M GOING TO SET FIRE TO EVERYTHING YOU LOVE."

(To be fair, this last form doesn't happen quite so often.)

John has never been a big drinker. There are too many bad thoughts associated with it. Growing up, John has seen his father come home drunk too many times, yelling and slurring and eventually passing out on the sofa. He's seen his sister, once she hit her teenage years, following in their father's footsteps, drinking and crying until she makes herself sick. These experiences put a rather strong association in John's mind of 'drunkenness' and 'bad things', and so, while some of his friends eagerly celebrated the day they hit the legal age of drinking by making up for seventeen years of sobriety in a single night, John was always happier being the designated sober friend. He could have just as much fun as the rest of them, and actually remember it the next morning, hangover-free.

However, this is not to say that John never allows himself the occasional drink. He won't go out with the sheer purpose of getting drunk, but he doesn't mind catching up with his mates at a pub over a beer or two, or having a glass of wine with dinner when he goes on a date. He's not stupid; he knows his limits, knows to pace himself, drink water, and he knows when he needs to stop. But that doesn't mean that John is going to outright refuse every drink he is offered. There is a time and a place for everything, after all. Times like today, the last day of John's exams, is definitely one such time.

So, when John's friends called him up and told him that he should get down to the pub for post-exam drinks, John accepted.

And when one of John's friends offered to shout him a drink when he turned up, because he'd been working so hard the past few weeks and he'd 'earnt it', John accepted.

And when another of John's friends later offered to buy him a second, to say thanks for the help that John offered him with his study, John accepted.

And – you can guess how the rest of the night went.

Which is why John is here, standing outside his room, banging on the door and shouting through the walls in the hope that his roommate will awaken from his deep, deep slumber and let John in.

John's key will still be sitting where John left it, on his desk, behind the locked front door. He's furious with himself for forgetting it, though this isn't the first time it's happened. Having a roommate that John spends a lot of his time with has lulled him into a false sense of security: on the occasions when John has forgotten his key, Bill has either had his, or has already been home to open the door when John knocks on it. Similarly, when Bill forgets his own keys, John's been able to let him in. The chances of both of them forgetting their keys at the same time and needing to call campus security are very slim.

The chances of Bill being fast asleep at three o'clock in the morning when John comes home without a key, however, are much less slim.

And Bill Murray can sleep through anything. John should know; one night, some idiot set the toaster on fire in the common room and set off the fire alarm, and John had to drag Bill out of bed by his feet before he even so much as stirred. It's been a joke between John and his friends for most of their university lives: if anyone wanted to assassinate Bill, they'd only have to wait until he fell asleep. The man could probably sleep through a bloody war if he tried.

Everyone else in the building, however, does not have Bill's supernatural sleeping abilities. The more John bangs and shouts, the more he can hear people moving around in his rooms, turning lights on. Some of them, further down the hallway, poke their heads out the door to see what all the commotion is about. Others simply yell "For God's sake, shut up!" through the wall. John would care, normally, but alcohol has a rather drastic effect on one's self-awareness. He only cares enough to yell the ever-creative comeback of "You shut up!" at one of the angry neighbours, but otherwise, his attention is focussed on waking up Bill, whatever the cost.

However, as the minutes pass, it becomes clearer and clearer that Bill is not waking up any time soon. At this point, it's probably safe to assume that everyone within hearing range is awake, but not Bill. John is exhausted – it's been a long night after a long week after an even longer month, and he's ready to pass out on his bed and sleep for at least ten hours straight. He barely has the energy to keep knocking.

It's at this point that he hears the sound of a door opening, and he has a joyous moment of believing that Bill has finally, finally awoken, before he realises that the door being opened is not his, but the one next door. John recognises the man standing behind it, but only vaguely. He's fairly certain he's had a class or two with him before, though he can't for the life of him remember his name, not at this point. He's also certain that he has never had any sort of interaction with him – not a conversation, nor even a nod of the head as they pass each other in the halls.

John doesn't care. At this point, an open door is an invitation.

John's neighbour does not look quite as groggy as you might expect from someone who has just been woken up. He's also fully dressed, which makes it clear that he's not been in bed. John doesn't know why the man would be awake and fully dressed at three o'clock in the morning. He also doesn't care. The only thing he does care about is the fact that John can see a sofa in the room behind the man, and John wants it.

So, John barely gives the man an opportunity to express his frustration in words before John is trying to stoop past him to get into the room.

Whatever the man had initially been about to say is reduced to an indignant sound. "What do you think you're doing?"

"Sofa," John says, as though that is a completely acceptable explanation.

"Yes, I have a sofa," the man says, side-stepping to block John's path before he can enter the room, "and no, you cannot use it."

John frowns, sticking out his bottom lip, and he leans against the door frame. It's difficult to stay standing, especially given that tilting his head back to meet the man's eyes is making him dizzy. Does the man have to be this tall?

"I need sleep," John says. His voice is slightly slurred. "Sofa's fine."

"I'm fairly certain you have a sofa in your own room," says the man. "And a bed."

John nods very seriously, as though this is a compelling argument to be pondered. "Good point," he says, and then he turns back to his own door, taking in a deep breath and once again starting to yell, "BILL-"

He barely gets more than a word out before the man grabs his arm, and John cuts himself off, looking first at the point of contact and then back up at the man.

"You're tall," he states.

The man ignores this, staring at John with an expression that is both thoughtful and exasperated. "Your roommate is not going to wake up any time soon, and you're just going to stand there and yell until you eventually pass out."

"I'm not going to pass out," John says. The fact that he's almost swaying on his feet makes this a lot less convincing. Or maybe the room is spinning. John can't tell.

"At least if you passed out you'd be quiet," the man says. "I'm not going to get anything else done if you're out here, so you might as well come in."

"Sofa?" John asks hopefully, and when the man nods his head he grins so brightly you'd think he'd just been offered the best present in the world.

The man steps out of the way and John eagerly moves into the room. Well, as eagerly as he can manage when the world still seems to be spinning, and he's still keeping his hand on the wall so he doesn't collapse. When he makes it to the sofa, he lets himself fall onto it face-first, and he lets out a happy sound at how soft it is, at how each of his muscles seems to be melting into the seat.

"You're the best neighbour ever," he says, but his voice is muffled by the cushion. He shifts so that he can turn his head, and then repeats it, emphasising the word 'best'.

"I'm really not," his neighbour says, regarding him carefully. "And if you throw up on my floor..."

"I'm not gonna throw up," John says, before the man can finish whatever threat he was about to make. "Just sleep. Bed time now."

The man sighs, and he may very well say something else, but at that point, John feels himself start to drift off. Given how tired he is, he doesn't even try to resist, and he's out in a matter of minutes.

OoO

John wakes the following morning and regrets all his life decisions.

He only opens his eyes for a second before he's squeezing them shut again, the light in the room too bright even behind his eyelids. His head is throbbing, and the rest of his body aches. He's in a weird position, lying on his stomach with his head elevated, neck turned to the side in a way that will leave a crick in it when he gets up. One of his arms has ended up wrapped around himself so his hand is against his upper back, and when he flexes his fingers he doesn't realise at first that it's his own hand touching him.

He doesn't realise where he is or remember what has happened. The only thing he's aware of is that he is sore and his bed is unusually uncomfortable.

The room is too loud, too. He can hear the sound of a chair creaking, and the sound of glass against wood, or the clicking and ringing of glasses that are gently tapped against each other. With his eyes closed, he's certain it's Bill making that noise, and really, is that necessary? Is it impossible for Bill to be a little bit quieter?

He manages to force his eyes open, prepared to tell Bill off for being so loud, before he realises that Bill isn't responsible for the noises.

The general layout of the room is exactly like John's. The view is wrong; John is used to waking up on his own bed, and having the view of the desk, but had John woken up on his own sofa, this is what he would have seen – his bed and his desk pressed up against the opposite wall. However, the layout is where the similarities end. The walls are bare of John's posters, instead only containing a large periodic table. Instead of piles of medical textbooks on the desk, there are test tubes and beakers and a Bunsen burner that John is pretty sure is supposed to be in the science lab. Sitting at the desk, facing away from John, is the person responsible for all the noise – a person who is far too tall and too lanky to be Bill, with hair too dark and too curly.

If John was more able to think straight, he might have panicked, because he's either not in his room or there is a complete stranger in his room, and who knows what weird chemical concoctions are being mixed together in those test tubes. However, John is tired and sore and his head feels fuzzy, and he's too busy mentally complaining about the pain to be worrying about this man's presence.

He tries to roll over into a less uncomfortable position, his muscles protesting with every movement, and he groans. The man at the desk does not turn around at the sound, but he does react to it. "Ah, you're awake," he says, in a voice that is much too low to be Bill's (just in case John had any lingering doubts). "I was beginning to think you died."

"Where's Bill?" John manages to ask. His voice sounds croaky, and he attempts to swallow to make his throat feel less dry. It doesn't do much.

"Probably in his own room, enjoying not having to deal with you groaning in pain every few seconds," the man says.

John frowns for a moment, though even furrowing his brow seems to make his head hurt more. "His room?" he repeats.

The man stops what he's doing, putting the test tube down on the desk, and he turns the chair to look at John, raising his eyebrows. "You thought you were in your own room?"

"Aren't I?"

"You were drunk last night. I thought you'd have at least some recollection."

The man is speaking perfect English, but it doesn't seem to make any sense in John's mind. He squeezes his eyes shut tight as he plays it over in his head, trying to work out what the man means. Why isn't he in his own room? He should be in his own room. Though his own room should have his biology textbooks and movie posters, not test tubes and the periodic table of elements.

"Recollection of what, exactly?" he asks after a pause.

"You were locked out of your room and you decided that my sofa was a better option."

John stares at the man's face for a moment, and then finally, something clicks in his head. Maybe he's finally waking up properly. "Ah, Christ," he mutters. "You're my neighbour."

"Finally."

John presses the heels of his palms to his eyes, wishing his head would stop spinning and throbbing like it's doing now. He can hear his neighbour moving around, but he doesn't open his eyes and pay attention to him until he hears the man say, "Here," and he opens his eyes to find that the man is now standing next to the sofa, holding a box of paracetamol and a glass of water.

It takes John a moment to find the strength to sit upright so that he can take the glass and the box from the man's hands, muttering a quick "Cheers" as he does. He pops a pill into his hand and then puts it in his mouth and swallows it with about half the glass of water. He almost spills some of the water down his face in the process, but he wipes it quickly with the back of his hand.

When he opens his eyes again, he finds that his neighbour is staring at him with a sort of intensity that makes John feel like he's under a microscope. He looks away for a moment to see if the man drops his gaze at the break in eye contact, but he does not.

After a moment, John asks, "What?"

The man takes a step back to slide into his seat at the desk, turning the chair so that it's facing John. "Just out of interest, do you remember anything from last night?"

The question is not one John wants to hear, because it immediately makes him feel like there is something important, or something embarrassing, that he should be remembering. "Please tell me I didn't do anything stupid," he says.

"That depends on your definition of stupid," the man says, and John wants to hit himself. Fortunately, the man continues, "If your mind has jumped to the worst possible conclusion, however, I assure you that you didn't do anything that would cause any sort of physical or psychological harm, to yourself or to anyone else. Although you may have angered a few people with how loud you were."

John isn't sure if the statement makes him feel more relieved or more humiliated. He hopes that whatever loud thing he was doing wasn't too terrible.

"Now," the man says again. "What do you remember?"

John rubs his eyes before responding. "I definitely remember going out with my mates," he says. "At the pub. They kept buying me drinks."

"Obviously."

"I remember taking a cab back and I remember getting out to come up here – but I don't actually remember getting up here or getting into my room. Well, your room. Obviously I'm not in my room." He frowns. He's not used to getting so drunk that he has blank spots in his memory. It's a little bit disconcerting. "That's about it."

The man hums. "Makes sense. You must have been exhausted when you got up here, given how quickly you fell asleep. Granted, you were banging on your door for at least fifteen minutes before I let you in."

"Yeah, um, sorry about that," John says. "Did you invite me in, or did I not give you that option?"

"I did invite you in," the man says. "Though that was mostly because you were desperate and I wanted to get some work done, which would have been made far too difficult if you had still been banging on the door."

"I really am sorry," John says. He feels like that's not enough, he owes this man at least a thousand more apologies. "I swear I'm not usually like this."

"Funny how often a drunken man will say that next day," the man says. "Alcohol doesn't change you, it just lowers your inhibitions."

John raises his hands to his face and rubs his eyes with the heels of his palms.

Then the man continues, "Do you always sleep talk, or is that just something you do when you're drunk, too?" and John immediately wants the sofa to open up and swallow him whole. He feels his entire face heat, and he's glad he'd chosen that moment to rub his eyes so at least his hands are partially covering his face.

"Oh, Christ," He mutters. "Please tell me I didn't say anything embarrassing."

Through the gaps between his fingers, he can see the man smirking. It makes him feel even worse.

"Most of it was rather ineloquent," the man says. "Your friends came up a few times. I think your subconscious was having a conversation with 'Bill'. Otherwise, it was a lot of mindless babbling."

"Thank God," John mutters. "Look, I really am I sorry for... taking over your room. I don't usually drink that much. I don't drink that often, either."

"Clearly."

"I'll go see if Bill will let me in now. Again, I really am sorry." Maybe he can find some way of making it up to the man. Maybe he'll buy him a nice box of chocolates to say sorry. Does the man like chocolates? Is that something he should ask first, or will that just sound weird?

He goes to get to his feet, groaning as his arms protest, but he stands too fast. The whole world is spinning and a second later, he's on the floor with little idea of how he got there.

This is precisely why he doesn't drink. He groans, pushing himself into a sitting position, and then he notices that the man has come over and offered him a hand. John considers refusing on principle, because he's never liked being seen as incompetent, but quite frankly, he's too hungover to do anything at the moment and it's not like he's going to make a bigger fool of himself than he already has. He takes the man's hand, relying on it a little more than he would like to as he gets to his feet. He would have tried to standing, to see if he could, but the man's other hand goes to his shoulder and gently guides him back onto the sofa.

"Maybe you should give yourself a moment," he suggests, crouching down and picking up the empty glass of water. John hears him take it into the kitchen, fill it up at the tap, and then he hands it back to John. John takes it and finishes the entire thing in three gulps.

"Ta," he says. "I really am sorry."

"And you've apologised several times now. It's getting redundant."

"Right, sorry," John says, and then cringes. "And sorry for saying sorry."

The man rolls his eyes, and returns to his desk, picking up a test tube.

John watches him for a moment, before saying, "I thought we weren't supposed to take them out of the labs."

"We're not," the man says. "But the labs are too busy for me to work in. Plus, the doors lock automatically after eight, so I can't work in there overnight."

"Why would you even be working overnight? Shouldn't you be sleeping?"

"Dull."

"But necessary."

"On occasion, yes. Most of the time, it's dull, and inconvenient."

John tries getting to his feet again, and has a little more success this time. He's a little bit unsteady, but he manages to walk the couple of steps between the sofa and the desk. He makes sure to put a hand on the back of the man's chair once he can reach it so that he has a little bit more support. If the man notices, he doesn't respond, which John takes to mean that he doesn't mind.

"What are you working on, anyway?" he asks, looking over the piles of lab equipment that the man has set up on the desk. He doesn't see any chemicals that could cause any severe harm or explosions, as long as the man knows what he's doing, which is a little bit reassuring. At least he can be reasonably certain that his neighbour isn't accidentally going to blow up the entire building. Or purposely blow up the building. Who knows what he's been up to last night?

"An experiment," the man replies, ever so helpfully, and John rolls his eyes at the vagueness of the statement.

"I thought chem only had assignments due in the middle of semester, not at the end."

"It's not for an assignment," the man says. "At least, not for a course. This is for my own interest."

"You stole test tubes from the chemistry labs for your own interest," John says. He doesn't phrase it like a question.

"I borrowed them," the man says, with emphasis on the word. "I plan on returning them when I'm done."

"Don't they usually count the equipment from time to time, to make sure it's not missing?" John asks. "I knew a guy who broke one of the beakers in our second year. Tried to cover it up, but I'm sure they found out within the next forty-eight hours that they were short one beaker."

"They make sure that all of it is in its rightful place during the semester, when they expect people to use the labs. They wouldn't bother counting them during exam period, especially given that they lock the labs."

John raises his eyebrows. "So, not only did you steal test tubes –"

"Borrowed," the man mutters.

"– but you also broke into a locked lab."

"It was hardly difficult. Took me less than a minute to pick the lock – I'm rather concerned about the security here."

"They probably don't feel the need to put particularly expensive locks on the lab doors," John says, "given that they wouldn't expect people to be breaking into them."

"Seems to be the case, though it's not a particularly well-thought out idea. There are plenty of dangerous chemicals in the labs. Choosing less complex locks just leaves open opportunities for people to break in and steal them with the intention of causing harm."

John hadn't thought about that, but now that the man has brought it up, he thinks it's a very good point. He hopes that the man is just particularly good at picking locks, and that it's not that the locks themselves are so inadequate that any particularly dangerous individual could get in and make something explode.

The man continues, "If you're going to try to appeal to my morality and tell me that I should return everything, don't bother. It's hardly as though I'm harming anyone, and they'll be back within a week."

John hadn't been planning to appeal to the man's morality. Whether or not this man had lab equipment in his room had no impact on John's life, and while John was usually a well-behaved student, he isn't about to turn into the sort of goody-two-shoes that goes around and turns people in for misbehaviour. Besides, the man "borrowing" test tubes for his own interests is hardly the worst thing that he could be doing, and it's not as though John has never done anything reckless. Everyone's got at least one story from university, after all.

The man's attention has returned to the test tubes, and John's gaze wanders around the room. He takes in the titles of the books on the desk – mostly chemistry, though there's a first-year psychology textbook hidden in the pile. He recognises the titles of some of the chemistry books as ones that he had used in previous courses, though some of them are unfamiliar. He wonders if that means that they're for a course that John has not taken, or if it is because they are books that the man has bought based on his own interest. Given the periodic table on the wall and the fact that the man is experimenting in his spare time, John is inclined to think that it's the latter: clearly, the man's interest in chemistry goes beyond that of your usual chemistry major.

"Are you looking for something?" the man asks, snapping John back to reality. He's surprised that the man has noticed that John was looking around the room at all, seeing as he hasn't moved from his position on the chair and has not so much as looked over his shoulder.

"No, I'm just taking in your room," John asks.

"Why?"

John shrugs his shoulders. "I don't know. Because I felt like it?"

The man puts down the test tube and swivels on his chair to face John. "You're standing now," he points out. "Is there any reason why you're still here?"

"Not really," John says. "You're experimenting. It's interesting."

Clearly, this is not the response that the man expected, seeing as he frowns, and his tone of voice indicates surprise when he says, "Is it?"

"Of course it is. I mean, I'm studying chem too, a bit, so I enjoy this sort of thing anyway, but the fact that you're doing this in your own time is interesting."

"Oh," the man says, and then he turns his chair back to face the desk.

John wants to ask what the man is actually doing – is he trying to make something in particular, or is he combining chemicals just for the sake of it, just to see what happens? The latter sounds like bad science when you put it that way, but that said, great science often comes out of people asking "What if?"

However, the man's attention has returned to his test tubes, and John can take a hint. It was nice enough that the man let John crash on his sofa; the least John can do is give him his space now.

So, John takes his hand off the back of the man's chair, taking a step back and giving himself a moment to make sure that he can stay standing now. The painkillers have kicked in now, which helps – his head isn't spinning quite so much, and he doesn't immediately fall to the floor, which in and of itself is an improvement compared to last time.

"I'll be off, then," he says. He goes to apologise again for last night before remembering that the man had told him to stop because it was becoming redundant, and so instead, he says, "Thank you for letting me stay last night. I mean, I know I didn't give you much of a choice, but – thanks."

The man doesn't respond, perhaps too engrossed in his experiment to pay any real attention to what John is saying, or perhaps silently hinting that he wants John to hurry up and leave and that he doesn't think John deserves a 'You're welcome'. Which is fair enough, really.

"Maybe I'll see you around sometime," John says in way of a final goodbye, and he turns to head towards the door.

"You live right next to me," the man says behind him, confirming that he has actually heard and processed what John was saying. "I believe 'seeing each other around' is unavoidable."

John smiles a bit. "I guess so. I'll try not to come barging into your room at three o'clock in the morning again."

"I'll only trust your ability to keep to that promise if you're sober."

"Don't worry," John says. "I don't plan on repeating this experience any time soon."

"Good," the man says, and he turns his attention back to his experiment as John steps out the door.

OoO

John finds out a few days later that the man's name is Sherlock.

John finds this out not from Sherlock himself, but from a rumour. Apparently, someone saw John leaving Sherlock's room, and somehow, that word spread, and the next thing John knows, it feels like half the school is convinced that John and Sherlock are together.

No attempts he makes at convincing people otherwise are successful, after that.