"Oi, Amy! Get down here, there's a sight to see!" the Doctor calls from the control room. "The Crab Nebula, about two thousand years after your time. I think you'd like it, blues and oranges and a hint of yellow!" He wrenches open the doors to the TARDIS and looks out into space. "Oh, it is a beauty." Then, "Amy! Come on!"

"On my way!" Heavy boots on the stairs behind him.

The Doctor turns, and when he sees her, he almost falls backwards out the open door.

She's wearing a typical Amy outfit, skinny jeans and a white top, but there's a very familiar blue bomber jacket over her shoulders.

"What. Are. You. Wearing."

"Oh, this? Found it in an old control room. Looks like TARDIS thought I might like it. Cute, isn't it?"

"Take that off right now."

"Oi, Doctor, I'm married." She raises an eyebrow playfully, but starts to take the jacket off anyway.

He glares, snatching it from her hands without another word. Hang on, he wasn't joking.

"What did I do?"

"That was never meant to be moved. Why did you have to pick it up? No, we'll put it back where it belongs." He slams the doors closed on the Crab Nebula, then races up the stairs and into one of the TARDIS's corridors.

"Doctor, whose is it?" She hasn't seen him this angry in a long time.

"Got to put it back just as she left it," he mumbles to himself. "Now where's that damn control room…"

"Doctor! I'm sorry! What's going on? What's so important about the jacket?"

"I'm not talking to you right now, Amy. I'm very angry at you. Very angry." He says it calmly, like stating a fact.

She follows him. "It was over there, that way. On the railing."

The Doctor opens the door to his old control room, a room for a different man and a different adventure. Orange and green. Sometimes he misses this room. It's been a long time; it's just as he left it. (Or it was, until Amy moved the jacket)

He marches over to the railing by the overstuffed yellow chairs. This jacket has hung here for so many years, and he never had any intention of moving it, not even touching it.

"Doctor, I'm sorry, I thought it was for me-"

"It was never for you. It belongs here." He presses it to his nose, gently, and smells again that familiar pefume, Rose.

Carefully, he sets her jacket back in its place.

"Please, just tell me what's going on," Amy says behind him.

"Go to your room."

"What? I'm not a child."

"Go. To. Your. Room. No supper."

Amy opens her mouth to protest, but the words don't come out. He turns, and the look in his eyes is distant. Old, unbelievably old. Sometimes she forgets the things he's seen.

This is a man who's seen everything, and it all comes down to a jacket on a rail in a room in a TARDIS that once belonged to her. He belonged to her. But that was a different man.

Finally, he lowers his eyes and brushes past Amy, out the door, turns the corner. And she goes to her room, as ordered.

Two hours later, Amy tentatively heads for the control room again. She peeks through the door, looking for the Doctor, and finally spots him. He sits in the open doorway, staring at the Crab Nebula, eating fish fingers and custard.

She knows he knows she's there, but his lack of response is a good sign. Amy goes to sit beside him, reaching for the custard bowl.

"You were right. It's beautiful," she says. It's her seventeenth nebula, but each one is different and each one is beautiful.

"I don't want to talk about her," he says. "So don't even ask."

"Doctor, I have to ask. There's so much I don't know about you, so many people you've loved and lost. It's been three years that I've known you, and far more for you. I want to know who that jacket belongs to."

There's a long silence, he considers her words.

"You know when you miss someone, but you forget and the pain dulls, and you go about ordinary life. Then you see something that reminds you of them, and it all comes rushing back and there's nothing you can do but let the pain wash over you. And you wonder how you ever forgot what it felt like to miss them."

She knows the feeling, of course she does. Rory died and she forgot him and then it all came back in that Roman camp, and she was crying and she didn't know why. So she understands. That jacket is like the engagement ring on the dashboard, it only serves as a reminder.

"Who was she?"

"The Bad Wolf." He smiles a little, gives Amy a sidelong glance. "It's a long story, from long ago."

"Then start talking. We've got forever."

"She said the same thing, and look how well that worked out."

Amy bites her lip, reaches for the Doctor's hand. "What… what happened to her?"

"What always happens. I lost her. Like I lose them all. But she was the first, the hardest."

"She died?"

"Oh, no, alive and well. But I can't ever see her again, and that's what hurts. I love her, so, so much. I was in a very dark place when I met her, and she... She was like starlight."

"But what about River?"

He dips a fish stick in the custard bowl, then pops it into his mouth. "Ewth wrt ra dffr prhn."

"Finish chewing," she says.

"I was a different person then."

"I don't understand."

"No one ever does." He smiles sadly.

"Where is she?"

"Trapped in a parallel universe with my human clone." At her expression, he adds, "I told you not to ask."

The silence falls peacefully between them.

After a little while, he says, "So dawn goes down to day, nothing gold can stay."

"That's Robert Frost, innit?"

"They never stay forever."

"I will."

"No, you won't. This is why I always bring you back to Rory. Because I can't lose you, not like the others. Some die, some are trapped in parallel universes, some lose their memories."

"Doctor, I want to stay forever."

"That's not how it works. Only I can live forever." He pauses, cocks his head to the side. "Wait, that's Voldemort. No, I just meant-"

"All right then, maybe I die. Maybe I get trapped somewhere you can't reach me. But I want you to know now, Doctor, that it's worth it. And I'm sure this girl of yours, wherever she is, thinks the same. There's nothing like this travelling. If, as you say, all things must end, then you have to know it's worth it, for us."

"Is it? I pick up these people, make them fall in love with me, and then ruin their lives."

"You don't ruin our lives. You make them worthwhile."

She gets up then, starts backing away from him. "Just think about it. The ones you leave behind, maybe it's not such a sad ending after all."

"I hate endings," he grumbles.

Amy walks up the stairs, towards the door to her bedroom. "I'm going back to my room. You need some time to yourself."

"I have millions of years to myself."

Halfway up the stairs, she pauses, turns back to the Doctor. He sits in the doorway to time and space, dangles his feet over the edge. "What was her name?"

He turns back to meet Amy's eyes. "Rose Tyler."