Summary: There are other universes out there and John Sheppard is seeing them all.
There is a universe where Sumner was never killed. It's not, as universes go, a bad one. In fact, in some ways, this universe has a definite advantage because John still got a team of his own and he was still was allowed to travel off world every week and get shot at. It was an ideal situation, all the fun and none of the administrative paperwork.
There is a universe where Kavanagh isn't a complete and utter dick. That is the only difference between this universe and John's. There are no big world changes as a result. Just a guy you didn't want to strangle and were sorry to see have his lower body torn apart because he accidentally stepped on an alien landmine while off world.
There is a universe where Jeanie is on Atlantis, while her brother is back home on Earth, entertaining millions being a world-famous concert pianist. John likes his McKay's Jeanie better. She smiles more and bits his head off less.
There is a universe where Rodney and Katie marry and John gets to be the best man, which is cool because he's never been a best man before. Not even when his only brother got married because even though he went, they were not exactly on speaking terms at the time. John gets to give Rodney that last minute pep talk when he starts to get cold feet. And Rodney actually listens to him, which is, of course, hilarious, because John is just as divorced in that universe as he is in his own.
There is a universe where he and Nancy never got married. There is a universe where they never even got together in the first place, because John had a couple drinks too many and when he went over to ask her to dance all she smelt was the alcohol on his breath and all she saw was his weaving gait and all she said was "no". There is a universe where he and Nancy never got divorced, where they had three kids, and tried to work it out but eventually ended up splitting up anyways because some things are just inevitable. There is a universe where they get into a shouting match and he pushes Nancy down the stairs and there is a universe where he sits with her at the bottom of the stairs as she silently cries and he promises never again. There is a universe where he keeps that promise and several where he doesn't. There is a universe where she leaves him but there is one where she doesn't. And there is a universe where he killed her. A universe where he went to jail and a universe where he got away with it. John tries not to care and tries to just move on because that isn't him. But it could have been.
There are universes where Atlantis doesn't exist. Or universes where Earth doesn't exist. Or universes where the Wraith don't exist or the Goa'uld or the Replicators or even the Ancients. There are universes with different adversaries, crazy ones that have never touched their universe, never will because they never were. But there is no universe without something that needs to be fought.
There is a universe where John doesn't recognize a single member of the senior staff of the Atlantis expedition. There are lots of universes where Atlantis doesn't have a John Sheppard. There is a universe where he never joined the Air Force. There is a universe where he never got in trouble in Afghanistan. There is a universe where he never went to Antarctica. There is a universe where he never sat in the chair. There is a universe where he flipped tails instead of heads and John's shocked to remember that his decision to come to Atlantis had actually rested upon the flip of a coin because in the end he simply hadn't been able to decide.
There are universes, predictably, where those who died, didn't. These should be the good universes, the happy ones, but, of course, there are just different dead, different names and different faces. And there are, of course, the universes where those who lived here, died there. John tries to pass these quickly because he knows all too well all the ways they've almost died. But he can't go fast enough, can't stop the tiny glimpses from coming through in high definition, and cannot close his eyes to this.
There is a universe where John's dad didn't die. In that universe he went to the hospital as soon as he started to have chest pains. In that universe they were able to save his. In that universe, John still doesn't speak to his father.
There is a universe where Torren is born with a cord around his neck . He won't breathe and he is this horrible husky blue colour. John tried CPR but didn't manage to do anymore then break his sternum when John applied too much pressure during his chest compressions. There is a universe where Teyla develops a post partum bleed and she losses over a litre of blood before anyone even notices and dies in Ronon's arms. And there is a universe where both these things happen and, even in the high tech facility that is Atlantis, they both die.
There is a universe where McKay ascended in a brilliant, white light. There is a universe where he returned, naked and amnesic in the gate room and there is a universe where he didn't. Or rather, hasn't yet. There is a universe where they are still waiting.
There is a universe where Ronon, at age eight, fell from a tree he was climbing and broke his neck. There is a universe where Ronon died on Sateda at the hands of the Wraith years ago, without even being made into a runner. And there are the many other universes where Ronon died as he ran. John is amazed that his Ronon is even still alive because so many versions of him are dead.
There are the universes that are that are nearly identical to his own, the differences so minute, so small, so insignificant, that they look exactly like his. Thousands... no millions... no billions and billions of universes that are just like his. And within those billions of billions of near identical universes, there are Sheppards, thousands and thousands of Sheppards, trapped in identical crazy Ancient devices, suddenly looking out at each other, and knowing that, probability speaking, that some are not going to make it out of here alive.
And then, there is a universe that is exactly like John's universe, down to the exact formation of molecules that make up his body. Somehow, someway, they look into each other's universes at the exact same moment and see each other, each in his own chair, in his own universe, with his own McKay working to save him and his own Keller monitoring his vital signs and they think, One of us is going to die and I don't know if it's me.
Later, McKay would say he wanted to be clear on one thing. He most certainly did not authorize this. This was something that his idiot scientists and his idiot friend did on their own and without his permission. In fact, he hadn't even been there when the piece had been discovered, an ancient chair that looked remarkably like the control chair. Except, he had pointed out to his overenthusiastic underlings after a quick overview of the scanner details, it obviously wasn't. This device, unlike the control chair which had access to pretty much every system in the city, was self contained. Even if they couldn't know what it was meant to do, they could be sure that it wouldn't make the city fly or manipulate the shield or fire drones, so, frankly, McKay didn't care. There were so many pieces of Ancient technology of unknown purpose, it was simply impossible to get excited over any one of them, especially if it didn't appear to have any engineering or military application.
McKay had handed the chair off to the handful of excited scientist who had found it and went back to do real work, like calculations for improving ZPM efficiency, and promptly forgot the device existed. Admittedly, he hadn't specifically said not to actually put anyone in the chair because he had assumed that was a given. After all, they were competent scientist with doctorates who did not need to be babysat, or so they liked to remind him.
Two weeks later, while he was in the midst trying to figure out why power demand on the ZedPM had increased suddenly, he got a call to come down to the room with the not-control chair. From experience McKay knew that this was just too much of a coincidence to not be a bad thing.
John was reclined in the chair, which appeared active judging from the glowing, with his eyes closed. Keller was already there, with a medical team, and John was hooked up to a heart monitor and an EEG, with a blood pressure cuff on his arm and a pulse oximeter on his finger. At least his staff was not complete idiots and had thought to call for medical help. They tried to explain what happened but McKay just waved them away in annoyance. It was obvious what had happened. They'd talked the Colonel into sitting in the chair, which honestly would not have taken a lot of convincing. He'd activated it, gone into a trance from which he couldn't be waken and now they couldn't shut down the machine.
McKay gave Dr. Keller considerably more respect by actually listening to what she had to say. Not only was she smart but she also tended to vote against idiocy, something that McKay appreciated. She did not want to remove Sheppard while the machine was running because, while there was no physical connection between Sheppard and the chair, there was some sort of mental connection between the two. She thought that moving him, especially when he was unresponsive and couldn't offer any verbal feedback, could cause unforeseen consequences.
All this meant that McKay had to try to shut down the machine before they could move Sheppard, which was, unfortunately, easier said than done. Not that McKay has any intention of mentioning that fact. Instead, he muttered and grumbled and snapped at the idiots who got themselves in this mess. Mostly he's pissed at John. These are newbies, after all, and if McKay decided not to send their asses home, they will gain a new appreciation for the protocols that are in place to prevent such missteps. But John, he should know better.
Eventually, the head of the chair moved into the up to the upright position but Sheppard's eyes remained closed and his body remained still.
"Colonel Sheppard? John?" Keller asked, forcefully, shaking his shoulder. When that didn't work, she rubbed her knuckles into John's sternum. Still nothing.
One look from Keller to Ronon, because of course Ronon and Teyla had to come down and crowd an already crowded room to observe the stupidity of their commanding officer, and he picked up Sheppard and on put him on the stretcher, where he was then rolled to the infirmary.
There is a universe where John Sheppard is alive and on Atlantis. Now, if only he knew which John Sheppard he was and which Atlantis this is. Obviously, he's one of those idiot Sheppards who let himself be talked into sitting into that chair. And, equally obvious, he's one of the Sheppard's whose McKay wasn't dead or back on Earth or faced with a concurrent emergency and was, therefore, able to get him out of the chair. However, he wonders if he's one of the John Sheppards who ended up with brain damage because though he can sense he was in the infirmary, can hear the heart monitor, smell the antiseptic and feel all those nasty uncomfortable tubes, he can't move. Not his eyes. Not his lips. Nor his fingers. He can't even stop his own breathing.
John gets regular visitors and he is glad when they come. He just wished he could tell his friends that. When they visit, they talk and John likes it when people talk. It helps to eliminate the possibilities. It helps him figure out where he is. He learns that this is a universe of Keller, not Carson. A universe of Ronon, not Ford. A universe of Rodney, not Jeanie. A universe of Woolsey, not Elizabeth or Carter or Sumner. This is a universe of Teyla, Torren and Kanaan. A universe of the Daedlus, which is going to take him back to Earth in two weeks if he doesn't snap out of it.
With each realization there is an elimination and this universe, the one that is his, becomes more clear, more real. He connects with this place, his place, his universe, his Atlantis. And the other Atlantis', the other hims, the other universes, fade. Not completely but enough for him to know that they are not his. One by one they fade until he can turn his head towards the nurse who is refilling his feeding pump and say, "Hi."
It has been two weeks and John is still not one hundred percent sure which universe he is in. That is kind of disturbing, when he actually stops to think about it so he tries not to. He's narrowed it down his current universe to a handful of hundred possibilities, universes so identical he may never know. The universes haven't faded completely, like John hoped they would. They float around in the back of his head. At night he dreams about those endless possibilities and wakes up confused and disorientated. Which universe is this?
John thinks that maybe if Kate was still alive, and there is a universe where she is, he would go to talk to her. Then he laughs at his own lie. If Elizabeth was still here, and there is a universe where she is, she would have made him go.
Keller told John he had been lying in the infirmary for twelve days while he tried to reorientate himself, after spending only twenty-three minutes in that machine. When Keller first told him that, he hadn't quite believed her. Those twenty-three minutes had felt like forever, like he had lived a thousand life times, which, in a way he had but Keller assured him that there was no permanent damage. No permanent physical damage, at least.