Spoilers: Vague for Doomsday.
Comments: I have just read through this whole comm, and I would like to say 'thank you, I thought it was just me'. I've seen all of Ten's run, but my only exposure to Eight is the movie, so apologies for any out-of-character that may ensue.
So at some point, somewhere after he’s had time to mourn – that’s a complete lie, he doesn’t think he’ll ever come out of mourning, but it’s been time enough to say he’s had enough time – something rather nasty clicks into place, a sequence of events going the wrong direction, and stops him in the middle of tinkering with the inertial dampers.
He grabs the console to keep from falling over, steadies himself, runs a hand over his face and through his hair. Of course. Of course. He’d always wondered how he’d been so prepared.
The TARDIS gives him that little high-pitched buzz that means she’s annoyed at him, whether for stopping in the middle of his work or for being about to do something not entirely possible he’s not sure.
“Relax, old girl. I must have done it before, so it won’t bend spacetime anymore than I usually do… when was I? Not Gallifrey, that won’t work, let’s try – ah-hah! Two thousand one was rather nice, wasn’t it.”
He finishes the wiring job without paying attention, and sets the TARDIS to Earth at the turn of the third millennium. Before he can think about it, he puts on his coat and heads out the door; the TARDIS is wistful-angry-resigned to what he is doing, has done, must do. She never wanted to be used this way, and who can blame her? But when a thing’s been done...
He’s in Los Angeles, of all places, he had had a strange weakness for America at this time, and he finds himself near the entrance to Chinatown, flirting with some woman that he must have met only today. He leans on a wall and waits to be noticed.
It doesn’t take long; his face may not be familiar to him yet but he is a Time Lord, and while that’s not as uncommon as it will be, it’s strange enough to draw attention. He looks up from his conversation and catches his own eye, starts, and makes his excuses.
He leads himself down a side street, a bit out of the way, and comes face-to-door with his previous self’s TARDIS. Which gives off a distinct air of disapproval.
“It’s not actually a paradox, don’t get yourself in a strop,” he tells her, just as he catches himself up. He gives himself a curious look with wide blue eyes.
He remembers being fairly strong by that age, but he can’t tell from looking. His younger self is all soft edges, velvet, wavy hair. He shakes his head; no point in feeling sorry for himself, even if himself really deserves it.
“You’re on speaking terms with my TARDIS,” he observes. “Have I forgotten something important again?” He trusts himself, without even thinking about it.
He shakes his head. “No, nothing like that. I’m you you haven’t been yet. You know how it is.”
A moment of confusion, and then he understands completely, and oh Rassilon the smile on his face, the one that looks like he’s just broken the code on the universe. He remembers looking like that. Still does it sometimes. Sometimes it’s not even deliberate. “Oh of course! Can I ask which?”
“Just two on,” he says.
He gives himself an appreciative look. “Tenth? It’s something to look forward to. But do I ever get to be ginger?”
“Not so far,” he says, and he shares a moment of amusement.
“But why are you here?” he asks. “You didn’t cross your own timeline just to tell me what my hair will look like.”
“No, I didn’t,” he says, and stops for a minute. The smile drops, and he feels the years since the War settle over his face.
His previous self looks confused, then alarmed, and settles into apprehension, all in the space of less than a second. “I suppose it was too much to hope for that it would be good news.”
“Is it ever?” he asks, and runs a hand through his hair. “No, I only ever get to pop ‘round and say ‘hi’ when the universe is about to come crashing down on itself. Not that it is! At the moment, anyway,” he says, and tries to will himself not to ask.
He asks. “Has it?”
He looks into his young, blue eyes, looking back at him with no comprehension. He’ll understand.
He doesn’t have to touch to use his telepathy on himself, but he does anyway: because he wants to know what that hair feels like from the outside, because it’s been much too long since he’s touched another Time Lord, because he thinks in a minute he’s going to need the contact.
He gives himself: the heartstopping fear of the last Dalek strike, his nerves burning with the heart of the TARDIS, the desperate need to end this, end it now, the roar of fire across a solar system, the sudden silence of a thousand thousand minds going out.
When he opens his eyes, they’re wet, and his younger self too is blinking away tears.
“What is that? What do I – what did you do?” he asks.
“That’s all I can give you,” he says.
His fingers are still on his temples. His younger self reaches up to him, taking his hands and pulling them downward, holding them between his own.
He’s not sure what he’s feeling – he doesn’t remember this – but he can guess, and he lets himself have the time to sort it out. Eventually, he looks up, the fear gone and replaced with a gentle smile. He was optimistic in this form, effortlessly confident.
“I’ll cross it when I come to it, and I’m not going to remember this,” he says.
He shakes his head. “Nothing but what I gave you, and you’ll only understand it when you have to use it.”
“That’s what you came here for.” He lets go, and misses the contact.
Suddenly, hands are at his collar, pulling him forward and down a little into a warm, gentle kiss. When he lets go, he’s smiling, both of him. His previous self is open about it; he can feel the surprise on his own face, but can’t help returning the expression.
“I forgot I got that from you,” he says.
He just keeps on with the smile and slides his hands around behind him, one on his neck, one at the small of his back. “It’s rather fun. I’m glad I get to keep it.”
He tries again, deeper, but no less sweet. He tastes like jellybabies. He is, and has been, a good kisser, though now he’s more forceful about it.
When he breaks off, both of him a little breathless, he says, “It’s going to be awful. It does get better, though. I don’t remember this, but I have to say anyway, it does get better,” he says.
“I believe you.”
He brushes his fingers past his temples one more time and takes his own memory with him, locking it off safe until it’s time to use it. He leaves himself alone with his TARDIS, darting around the corner before he can ask himself any more questions.