The coin was lying on a shelf with a small handful of others, scattered amongst photo frames and other odds and ends, obviously dropped there and forgotten, far from legal currency anywhere in the Pegasus galaxy. It caught McKay's eye as he slouched on the sofa waiting for Carson to come back with food, in the way that small things become hugely fascinating to a bored mind.

Larger than the others, shiny, bi-metallic with a gold rim and silvery centre plug, it was strangely attractive as coins went. It was obvious from the visible side that it had arrived with Carson from Earth; the head of Queen Elizabeth II stared blankly off into the distance, apparently fixated with something McKay couldn't see. He reached out lazily and plucked the coin off the shelf, turning it over in his fingers. What was it that made foreign coins so fascinating? He still had, somewhere, a pot of miscellaneous loose change collected over the years from various jaunts abroad, worthless denominations that he was oddly reluctant to part ways with. He had no plans for them, no intention to expand his collection, and no sentimental attachment to them, but they remained on a shelf back on Earth, gathering dust.

McKay thought about coins, but his subconscious had a suggestion it was attempting to make heard. It was very similar to the suggestion it had presented when Carson first offered dinner at his place that night, and again when he was helping Carson in the kitchen (mainly by getting in the way, dropping things, and offering smart-ass comments about the quality of the prospective meal).

This time his subconscious, which was usually insistent about these things right up until the moment McKay screwed up beyond hope of repair, was suggesting a compromise. It was inspired by the coin, and the warm smell of something spicy coming from the kitchen, and the memory of the tired but tolerant look on Carson's face when he finally banished McKay from said kitchen. It also derived from remembered analogies in popular science books, which he had mocked when he first read them but felt an odd affection for now.

He rubbed the coin between his thumb and forefinger, examining the concentric patterns on the reverse side, then, without much real enthusiasm, attempted to push the middle of the disc out of its setting. If he procrastinated long enough then Carson would appear with dinner and he'd forget the coin and once more repress the insidious desires that had slowly been creeping their way into his head ever since Antarctica. But…

He flipped the coin once. It was very flippable. Its weight meant it wouldn't fly away across the room, and after three slow turns in the air it landed with a satisfying slap in the palm of his hand. He curled his fingers over it, unwilling to look at the result, and instead turned his head towards the kitchen and tried to infer, from the various culinary sounds emanating from that direction, how long dinner would be. After a long moment it began to appear that he would have to look at the coin, but Carson came to the rescue.

"All ready, Rodney," he called from the doorway. "Come and give us a hand."

As they laid out the table – something Rodney hadn't done except under protest, as a small child – the coin stayed palmed and hidden. As he placed his own plate on the place mat, he did two things; firstly he allowed himself a small smile, because here was a single man in possession of place mats, and that definitely increased his chances of not getting punched tonight; and secondly he slipped the coin under his plate, making sure not to turn it over in the process.

Carson had cooked something with meat caught by Athosians on the mainland, which Rodney had never eaten before and treated with great suspicion, peering at it like a desperate man who's just discovered a potentially poisonous snake in the toilet. As Carson pointed out, it was very unlike him to treat food with anything approaching mercy, but, he rebutted, it was also unlike him to ingest alien life forms.

"Relax," said Carson, "it tastes like steak."

"Steak? Oh. Good."

Carson waited until McKay had stuffed a forkful into his mouth before adding, "aye… badger steak."

Instantly, McKay could see what he meant despite never, as far as he knew, having eaten badger. Part of him wondered whether Carson was also guessing at the comparison, but most of him was fighting against the desire to spit the coarse, foul-tasting meat back onto the plate. He forced the mouthful down, then grabbed his glass of wine to get rid of the taste. He paused with it half-way to his mouth.

"Is this from the damned Athosians too?"

Carson smiled and shook his head. "Sorry, Rodney. I didn't realise it would be so bad."

"I thought you said you'd tried it before?"

"Not this particular dish, but usually their recipes turn out very well…"

"Ugh…"

Apparently out of some sense of duty to his cookery teacher on the mainland, Carson attempted a few more mouthfuls of the meat, while Rodney wolfed down his vegetables and sulked. A combination of nerves and a weird sense of anticipation had served to keep hunger at bay all day, so that now he was absolutely starving. Starving always made him thoroughly miserable, and even Carson's attempts to keep the conversation going were met with sullen sarcasm and a complete lack of enthusiasm that might have put a lesser man off. Carson knew Rodney well enough to realise that it wasn't the company that put him in such a bad mood, and gallantly handed over some of his own potatoes and salad. Rodney had nearly cleared his plate again before the implications of the gesture dawned on him, and he became aware once more of the hidden coin, waiting patiently to determine his fate.

Carson put down his cutlery and toyed with his wine glass. He hadn't touched a drop, but he topped it up anyway. Displacement activity, McKay thought. He wants to say something…Oh God, he wants to say something…

The moment dragged on with Carson apparently trying to find his tongue and Rodney holding his breath in case exhaling was enough to jolt his friend out of his reverie. He could imagine the coin under the plate, glowing red hot, burning its way up through the metal and revealing itself for all to see. The not knowing was both agonising and a beautiful blessing at the same time.

"Sometimes I wish I'd never come here," said Carson eventually. His gaze remained fixed on his glass, his fingers tracing the intricate patterns cut into the stem. "I wish I'd just bloody well gone home and got a proper job. My mum cooking me dinner, dates with nice, normal girls, a pretty good chance of growing old…"

Rodney blinked. This wasn't what he had expected. He tried to line up some comforting sounds, or a suitable joke to make light of their collective situation, but they wouldn't come. Not because he knew how Carson felt – he didn't. Not at all. He was simply stunned that anyone with a scientific mind could come to Atlantis and want to go home again. There was something in this new galaxy to satisfy someone working in any branch of science, even medicine – after all, didn't Carson Beckett have the best Wraith research lab in the known universe? Did anyone know more, biologically speaking, about the alien species than him? That was something to be proud of, surely?

Carson took a deep breath, and it seemed to Rodney that he was wearing the same expression that accompanied him out of the operating room when luck and fate simply hadn't been on his side. "Sometimes," he said. "I usually don't let it get to me. And besides, there's so much scope for opportunity out here-"

"Yes," McKay interrupted, before Carson could veer off down Melancholy Street again. "For example I'm in the middle of developing a-"

"I don't mean scientifically," Carson amended. "Can't you feel it? There's a sense of freedom here that you don't get on Earth. Even in Scotland."

McKay managed to bite back a culturally-orientated quip that he would happily have let loose on anyone else at that point. Instead he managed a kind of facial shrug.

"Yeah, sure. Being hunted by the Wraith, tortured by the Genii, bullied by most of the indigenous people we come across, attacked by mindless creatures, tricked by the stupid technology, not to mention fed this – this offal I wouldn't give to my cat… That's real freedom, that is. I feel so very, very liberated, and I'm glad you feel it too."

"We're in the city of the Ancients," Carson insisted. "There's no cultural human constraints here, except for those we impose on ourselves. The only laws are those we've brought with us, and there's nothing to keep us within the imposed jurisdiction of such laws. All of us here, on Atlantis, are truly free."

McKay was not renowned for his people skills, but his intelligence had to count for something. "That's what scares you?"

"If I'm honest? Aye. And not only that, but there's a pressure on us so long as we remain here in the city. We have to aspire to the Ancients, to be as strong and wise as them, and if we can't, then we fail the entire galaxy. That wasn't exactly one of my career goals when I went to medical school."

McKay shook his head, more to clear it than to disagree. He had come here expecting an average meal and some inane conversation, before heading home to bash his head against a wall and ask himself, yet again, why he didn't just pluck up the courage and broach the subject he most longed to. Instead, Carson was talking gibberish. Not that that was entirely new – McKay felt no shame in admitting that the complicated and inescapably gooey workings of organics meant almost nothing to him, although, naturally, he was sure he could figure it all out if he was ever bored or desperate enough to try. He had never heard anything like this from Carson, though. Doctors don't make good philosophers, and it was his opinion that they shouldn't even try, for the sake of humanity. Hearing Carson talk about moral freedom and the fate of the galaxy was entirely unsettling, and…

Oh. Oh. McKay slowly raised his gaze so he could look at his friend for the first time in a long while. Properly look, not just glance, or sneak a subtle peek when Carson was bending down for something. What he saw was a vulnerable man making a complete cock-up of an attempt to lay himself emotionally bare.

Moral freedom, McKay mused. Interesting…

"I'm sorry," said Carson eventually. "I'm being silly. I really am glad I came here, most of the time." He lifted his gaze and offered a smile. You daft bastard, thought McKay.

"Good," he said. "Er. Good. Me too." He waved a hand. "Even if the food is terrible…"

"Aye." Another smile, its dimensions calculated just right to trigger a response in an interested potential partner, signs which McKay was certain to miss until way, way too late. "Well. We'd better clear this lot up, then."

Carson moved round the table to take McKay's plate first, but he was on his feet in a flash, one hand holding the plate down on the table. "Wait!"

Carson looked alarmed by the sudden movement. "What is it, Rodney?"

"I tossed a coin." This was met with a blank expression, and as usual McKay realised he would have to waste time explaining a complicated process to a simpleton. "You were talking about moral freedom," he said, "and I thought, you know, freedom from expectations and cultural norms, but you're wrong, because, heh, with the US military hanging round this might as well be the far-flung fifty-first state, and anything anyone does is going to be judged at some level by their standards, and, well, to be frank I don't like those guys. The major's alright, obviously, and Ford, and, uh, actually I don't really talk to any of the others… But they're a bit threatening, really, with all those guns, and… That's why I tossed a coin."

Carson continued to stare at him as if he'd suddenly started speaking Dutch. "What coin?"

"Shiny one. I found it. But that's not the point."

"Then what is the point? Assuming there is one at all."

McKay stared back at him. It was beginning to dawn on him that if they both continued to edge around the matter like this, nothing was ever going to come of it, and it was probably time to spell his intentions out in English so plain that even a Scotsman could understand it.

"It's all about the relative state interpretation of quantum mechanics," he said.

"…Rodney, I just want your plate."

"No, shut up, listen! If you have an indeterminate quantum system, and you observe it, you cause it to collapse into, or select, one determinate outcome, because the act of observation is inherently deterministic and… Look. For every decision that's made, by every single individual or object in the universe, a multitude of new universes come into being, one for every possible outcome of a situation."

Carson raised an eyebrow. "Trouser legs of time," he said.

McKay frowned. "From now on you only read sci-fi if it's been vetted by me, but yes, that's one popular misconception of a hugely complicated theory. Now shut up again."

"Sorry."

"Shush. Where was I? Right, universes. You toss a coin, don't look at it, and you've spawned two alternate universes – one in which the result was heads, one in which it was tails. Once you look at the coin, the balance collapses and you're left with only the most probable of the two universes, where the coin shows either heads or tails. Until then the coin must be at once both heads and tails, because neither is more likely than the other. You look, you cinch the deal. Right?"

Carson gave him a resigned look. "I think I follow."

"Well I tossed a coin. And I haven't looked yet. And it's under that plate."

They both stared down at the remains of McKay's meal. Rodney was suddenly reminded how hungry he still was, but just this once food could wait.

"Well if it'll mess up your experiment, how about you shut your eyes and I'll put the coin somewhere else you can't see it?"

"No, no, no! It's not specifically me. I'm not a magic quantum wavefunction collapser – if you look, it's decided just as permanently. Leave it alone."

By the look in Carson's eyes, McKay could tell the doctor was getting tired of this conversational detour. As Carson turned away to pick up his own plate, McKay was at once both relieved and appalled to hear his own voice shouting a lot louder than necessary.

"I tossed a coin to decide whether I should try and kiss you tonight!"

Carson froze, his eyes wide like the proverbial deer for whom the light at the end of the tunnel is an approaching Jeep. An instant later he picked up his dinner plate and the empty wine glass and the full wine glass, and then he took them through to the kitchen area. McKay stood very still and listened to the sounds of washing up. He knew he should offer to help, but he also got the impression that Carson had left the room for a reason, and that the reason was quite likely to do with him.

Eventually Carson had to come back. He leaned in the doorway, looking tired and lost and hopelessly handsome in the dim light.

"Heads or tails?" he said.

"What?"

"Am I heads or tails in this wee experiment of yours?"

"Uh. Heads. And it's not an experiment."

Carson seemed to consider this answer, and McKay hoped he wasn't interpreting 'heads' and 'tails' as homosexual euphemisms, because he had his own opinions on that front. Eventually he folded his arms.

"So which is it?"

"I can't look."

"Well, I can't stand here all night."

"Fine, then. You look."

Carson strode across the room, and McKay screwed his eyes shut. He heard the plate move, and he heard a faint, non-judgemental 'hm'.

"So which is it?"

"Open your eyes."

"Just tell me!"

There was a sigh of breath against his jaw, then dry lips touched his own. He was about to lean in, to grab Carson and turn the chaste kiss into a proper, grown-up, x-rated embrace, but the pressure was suddenly gone and Carson took a step back.

"This is what I was talking about," he said. "What I'm so very afraid of. It would be so easy for me to go home, and leave this part of myself behind me, and I'm not even sure I'd regret it."

"I would," said McKay, too quickly. "And anyway, you'd be just as gay in Scotland as you are here."

"Aye. But my biggest source of temptation would be three million light-years away."

"Oh," said McKay, with an impotent glance behind him, in the direction of the main bulk of the city. "You mean there's someone…"

"You're a daft bugger, you know that?"

"…Oh."

Silence fell and stretched out between them. Carson stared out of the window, into the infinite black of night, and McKay was suddenly intensely interested in his own shoes. His mind was moving quickly now, presenting him with a hundred different prospective outcomes of this encounter, a hundred ways for their relationship to change, and not one single way to control which outcome they got.

"We don't have to tell anyone," he said. "And anyway, like you said, it's not like we're breaking any laws, or our parents are going to walk in, and, heh, all the research suggests the Ancients were very liberal-minded. Something to, uh, aspire to, learn from, perhaps?" He forced himself to look up at Carson. "Just… don't say you'll think about it. I couldn't handle that. Tell me to go and I'll go, but don't leave me hanging."

The lights seemed to dim a little more, but in reality it was the city powering down for the night. Outside the window McKay could see individual lights switching off, and the stars stood out brighter in the night sky. He had never felt so far from home in his life than in that moment. Hungry and tired and acutely aware of how fragile his own heart could be, he suddenly understood what Carson meant. He could see the future stretching out in front of him like a road through the desert, stiflingly dry and lonely, an adventure without hope of returning to the past and the safety of home.

Then arms wrapped gingerly around his waist, and he found himself being hugged. He hadn't been hugged in years, if ever, and he certainly hadn't been hugged like this by Carson before. Strange as it was, he felt a familiar rush of sensation not un-akin to the thrill of a much needed rain storm.

"I could never ask you to leave," Carson murmured. "Well," he added, and McKay felt him smile against his cheek, "not unless you were being really annoying."

"Hey! I resent that…"

Rodney didn't protest for long, because there's only so much you can complain about when the person you've wanted for over a year is tugging insistently at your lip with his teeth. He gave in with a sigh of relief, and let Carson decide his fate for a little while.

Later, with the lights dimmed, Carson slid out from under a possessive arm, and pulled on shorts and a shirt. He smiled as Rodney murmured something unintelligible in his sleep, then rolled over, but there was no way Carson could drift off and leave his apartment in such a state. He busied himself with clearing up the remains of dinner, then threw yesterday's clothes into a basket to be cleaned, and folded Rodney's clothes over the back of a chair. He took one last look around the room, and noticed the two-pound coin still sitting on the dining table, forgotten and untouched, its concentric circle design laid bare to the ceiling.

He picked it up, then put it back on the shelf where it belonged.