It really is a complete and total accident, because all he's trying to do is fix a bit of faulty wiring in the TARDIS, right? And he'd no idea he was so close to anything dangerous, what with it being in the broom cupboard. Then again, maybe he should have known, seeing as the broom cupboard had anything in it that would have faulty wiring in the first place. Moot point at the moment, though, what with the sudden snap, quickly followed by gas spraying straight in his face.
Thankfully, the effects are not immediate, and he has time to seal the hole up with the sonic screwdriver before he starts feeling even the slightest bit off-kilter. As he hurries down the corridor toward the console room he thinks he might even have managed to hit something innocuous for once, but as soon as he bursts into the room, he knows he's wrong. He's hit all at once with such an overwhelming barrage of sensations that he very nearly falls flat on his arse.
Instead, he braces himself against the wall and lets his body slide down, only caring that he's in a position where he can safely lie still until his mind calms back down again. He stares out in front of himself, knowing that even so much as turning his head is only going to invite further stimuli and more sensory information. It's fine, for almost a minute, he's pretty sure, because all he can see is the console. And yes, maybe it's sort of swimming in his vision, out of focus and multiplying. One second it's hexagonal and white, clean lines that remind him of younger days, and then it's darker, with a wood finish. A flash of green light grows steadily brighter and then resolves into a quieter blue with a lot of fiddly bits.
And that's when it all goes to hell. Amy and Rory come flying into his line of sight, looking concerned, and the Doctor appreciates it, really he does, but it would all be so much easier if they'd kindly go away for an hour and let him remember in peace. Of course, being the good companions that they are, they stay there and fuss over him, saying things that he can almost make out if he concentrates very hard. Best not to, though, not if he can help it.
He directs his attention to Amy first, mostly because Rory is suddenly gone, though the Doctor feels hands on his body and assumes Rory is trying to muddle his way through discovering what's wrong. He's momentarily disoriented by hands everywhere, faces of dozens of doctors floating by, asking how he's doing, telling him not to get up, 'I say, you gave us quite the scare, old chap' in Harry's perpetually-worried tone.
The Doctor smiles slightly at that, and thinks maybe he mumbles Harry's name before he shakes the memories away and focuses on Amy's concerned face filling his vision. There aren't nearly so many memories bound up in her as there are in the TARDIS, but they're also all more recent and therefore much more easily recalled. They're also incredibly vivid. She's looked at him dozens of times with exactly that look on her face, when she'd thought him dead, when he hadn't known how to fix whatever situation they were in. She's looked at him more ways than he can count: confused, horrified, happy, excited, tired, infatuated. And she's touched him, too. Kissed him, hit him, clung to his hand, hugged him....
She drifts out of his line of sight, and Rory's back, shining a light in his eyes, presumably to check his pupils. And that's good, he'll undoubtedly notice the dilation and maybe work out that there's a drug in play here, not that he'll be able to do much to help. Once the light is gone and the spots clear from his eyes, the memories start coming. At first, it's the same kind of thing he'd seen from Amy. Anger, jealousy, surprise, pleasure, a whiff of cologne, nurse scrubs, waking with their foreheads pressed together.
But then, it takes a turn for the weird. He flashes on Rory dressed as an Aztec warrior, hovering on the edges of a crowd. And that's...not possible. Not since he's only been there once, back when he'd just left Gallifrey and still had Susan with him. Before he can even try to parse a meaning, his mind skips on to another memory.
This time Rory looks like a giant toy soldier, and he's chasing the Doctor. Rory's never looked at him like that before (at least, the Doctor thought he hadn't), like he legitimately wants the Doctor dead. Besides which, that place hadn't even really existed, so how could Rory have been there?
Another flash, and there's Rory dressed as a UNIT soldier, then walking out one door and reappearing through another across the main room in Castrovalva. Dressed as a Time Lord and observing the Doctor's trial from just behind the jury, then a hollow-eyed resident of Paradise Towers, a vampire at a New Year's Eve party in 1999, a glimpse of a shadowy figure on the surface of Midnight...
The Doctor splutters a little, the memories receding under the shock of water being dumped on his head. He tries to wipe his eyes clear, and only then realises that his arms are being held down. He lets his arms fall limp, and when the pressure on them eases, he takes the opportunity to slip the right one out of his jacket sleeve and swipe it across his eyes.
Naturally, the first thing he sees is Rory's face, still looking worried and not at all like he knows what he's doing. "What are you?" the Doctor yells, scrambling backward frantically, not taking his eyes off of Rory, not even for a second. Rory actually looks confused, and it only ratchets the Doctor's anxiety up higher. "You were an Aztec!" The Doctor begins ticking things off on his fingers. "A UNIT soldier, a Castrovalvan, a Time Lord, a..." the Doctor stutters to a halt. "You were the thing of my nightmares, that...that thing on Midnight."
"Doctor, what-" Amy begins, but she stops talking when Rory shakes his head.
"How could you know all that?" Rory asks quietly, a bit shocked.
"That's just not possible. You couldn't have been in all of those places, you just couldn't." The Doctor ignores Rory's question and curls in on himself a little, grateful that neither of them have made a move toward him. It's very possible the drug is still affecting him, because he's finding it difficult to think the situation through, to come up with a reasonable explanation for how Rory could have been stalking him throughout all of his lifetimes.
"Doctor, you need to calm down. Whatever drug you've got in your system is increasing your heart rate drastically. You probably know better than I do what could happen if it increases too much, but I'm willing to bet it's not good."
The Doctor twitches while Rory speaks, anxious for an explanation or a means of escape. "Answer my question!" The Doctor can feel his hearts pounding, now that it's been pointed out, and Rory is undoubtedly correct in his assessment of the situation. Not that that makes it any easier to calm down.
"I'm a human, Doctor. Just like I've always been."
"No, you can't be. But what could you be? Time Lord would be the most obvious, but I would have known about that..."
"When I got sucked into that crack in the cave, it...did something to me. No one seemed to be able to see or hear me, and I just sort of jumped from place to place. Best I could tell, I was either dead or outside of time."
"Outside of time? But then how could you...of course! You existed where and when I was because I was the only one who could remember you!"
"You remembered me?" Rory sounds surprised by that bit of information. “That's how you knew where I was. But you obviously didn't look like you do now, which is why I didn't see the connection. And here I thought I'd just got the opportunity to see lots of new places without the fear of dying round every corner."
"Sorry." And he is, for a lot of the things that have happened since Rory came aboard the TARDIS, but most definitely for not being able to keep Rory from non-existence, though obviously that hadn't quite happened as he thought, either.
Rory looks taken aback for a second before he pulls himself together. "Right, well. I'm sure we can talk more about that later. If you're feeling up to it, we should get you to the infirmary, where you can show me what I should be doing to treat this-" Rory gestures vaguely at him, “drug? Or whatever it is that's happened to you.”
The Doctor struggles to sit up, because Rory is right, and the sooner he can get this out of his system, the better, even if it's affecting him more physically than mentally, now. Suddenly, arms are supporting him from both sides, and the Doctor turns to the right, only then remembering that Amy has been here the entire time. She looks back, and it's clear how many questions she has, and accusations, maybe, but she's also obviously too worried to ask any of them now. Just as well, since the Doctor really doesn't feel up to explaining.
His mind is getting clearer, and the memories have begun to fade back into the recesses of his mind where they belong, but it'll be hours, at least, before he's fit to do anything more than lying still or sleeping. In the meantime, he supposes, he can try to work out what he's going to say to his companions. Sometimes this life is a little too strange, even for him.