A/N: Missing scene set between the Doctors leaving the dungeon and arriving in the Zygon control room.
Despite getting somewhat upset with each other over the issue of children on Gallifrey, Ten and Eleven seemed to get on alright after that scene. I figure some smoothing out must have taken place, and in my head, this is how it went.
Alas, nothing is mine, much as I really really wish it was. Property of the BBC and all that. Sigh.
Unable to stand it any longer, the Doctor heaved an exasperated sigh and spun around on his heel. "What?" he demanded.
The gaze in his younger self's eyes that he had previously felt boring into the back of his brain hardened into a glare. "I can't believe you actually forgot," he said.
"Really? Now?" he asked, gesturing to the possibly-Zygon Elizabeth and the definitely-Zygon guard herding them up a flight of stairs. "Slightly more pressing things happening."
He resumed walking, but his younger self fell into step beside him. He sighed. He knew he shouldn't have thought he could get off that easily. "Nearly two and a half billion," he hissed. "And you forgot. Is four hundred years all it takes?"
"I told you, I've moved on," the Doctor replied. He chanced a look into his counterpart's eyes and found himself on the receiving end of that look. Oh, but he remembered that one—such great hopes crushed by complete and utter disappointment. He'd never thought what it would be like to have it directed at him, and blimey, he'd never had any idea it was that effective!
"You're right," the younger one said coldly. "I really don't want to know where I'm going."
He looked away, and the Doctor swallowed hard. This was ridiculous. They were in the middle of a very complicated paradox and there were Zygons trying to take over the world—he didn't need to explain himself to himself! He sighed. Yes. Yes, he did. "It's been a long four hundred years," he said softly, loud enough for himself to hear but too quiet for their guards, Clara or the…other one to hear. "I just…" There was so much he wanted to say, to explain being hunted by the Silence and what that did to the people he loved, to speak of the loss of Amy, Rory and River, of the times he failed to save Clara—there was so much he was desperate to make himself understand. "It hurt too much," he said finally.
"We don't deserve for it not to," the younger one said curtly. "No matter how many years it's been."
"You think I don't know that?" he snapped back.
He received an incredulous raised eyebrow in response. "But you forgot anyway?" It was more of an accusation than a question.
"Of course I didn't forget!" he retorted, barely able to keep himself from shouting. Sweet Rassilon, he was infuriating! He rounded on himself with the full force of the Oncoming Storm in his eyes, pleased underneath his anger to see the younger one stop short at the fury on his face. "There were two billion, four hundred seventy-three million, nine hundred eighty-one thousand, six hundred and sixty two children on Gallifrey the day we burned it," he snarled. "And buried in the heart of the TARDIS there is a room where each of their names is scratched into the wall. You were the one who counted them, but by the time we got around to me, it wasn't good enough any more to stop there. I. Never. Forgot." He turned his head away with a growl, his pulses pounding in his ears.
They continued their march up the stairs in silence for some moments as he knew his younger self was processing this information. "Then why tell us you forgot?" he asked at last.
The Doctor sighed. He hadn't meant to say any of that. No wonder he had fought this regeneration so hard. Who would want to turn into the bitter old man he sounded like? "Rule One," he said with a humourless smile. His younger self raised a questioning eyebrow. Right. Probably too early to be quoting River, wasn't it? He sighed again. "I wanted you to think you had hope," he said at last. "After the Time War, we just…well, we just kept losing things, didn't we? And you were always—don't get me wrong, I really did love being you, but you were always the sad one. I wanted you to have some more peaceful days to look forward to."
His other self smiled sadly. "Thanks, but you know it's never a good idea to lie to yourself."
"It wasn't totally a lie," he protested. "I haven't forgotten, but I…I don't remember all the time," he said, a fond twinge in his hearts as he remembered Rory saying those same words a long time ago. "It lets me carry on, but it doesn't make it any less meaningful when I do remember."
Somewhat to his surprise, the younger one nodded. (He remembered being much harder to convince about things.) "Remembering things some of the time," he said, half to himself. "I suppose that's fair. Four hundred years more, it's nice to hope we may have earned that much," he admitted, sounding much more begrudging than the Doctor knew he felt. Something in his step had lightened, now that he knew he need no longer fear the man he was going to be.
"Quite right," the Doctor said. "And as I was saying before, much more pressing things at the moment…"
"Yes, right," his younger self agreed, straightening the lapels of his suit. "Zygons and paradoxes and such. Zygons first, d'you reckon?"
The Doctor grinned and nodded. "Yeah. Let's get the easy one out of the way."