"I'm sorry," said the old woman as she looked into the wall. "You'll have to run this by me again. That's you in there. It is!"
"No," said the woman beside her. "She's the Doctor, like I said. It's not the same."
"But her face—"
"Well, yes, that bit's the same. And her past, mostly. But in a way she's like everything here. What we should be; what we really are. It's all out there, and here we're all able to see it. But we can't ever be it, not really. We can only watch on through the wall."
The old woman screwed up her face as she tried to follow along.
"She's like your shadow?" she said.
The Doctor laughed. "I'm hers! A nightmare someone had of her, before she was fully formed. It's all a bit complicated, I'm afraid."
The light was extremely bright in the space between the walls, drowning out even the shadows. The Doctor took out her torch and it shone bright, too, though its light was near drowned out against the glare.
"The Doctor's universe is built on hope," she said, "but ours is a world that's made up out of fear. If there were places she couldn't come to, or couldn't see"—
She hesitated, unsure how best to explain.
"Were you frightened as a child?" she said to the old woman.
The woman beside her frowned, looking round to the pressing hands of light.
"Of course I was," she said. "Don't you know what happened?"
"I think so," said the Doctor. "I'm pretty sure I do."
"None of us thought there was any way that things could turn out okay. But they did, of course. It all comes out right in the end."
The Doctor nodded.
"Yes," she said. "That's the story that's kept you safe. But it's not always good enough for a child. Sometimes they need a story as big as her there in the wall. For their own fears, their own lives. And if they were to tell that story in their minds"—
She shrugged.
"Then all of it is stories in the end," she said. "It all has to happen somewhere, that's the rule. He might not have written that book you like, if he'd ever known. Then so many lives would've been saved."
She paused.
"Though of course," she said very quickly, "it's not always a child who's calling. If someone somewhere had thought it, that when she was needed, when it was time"—
"I am trying to keep up with you," said the old woman, "but I'm still not sure I follow."
"Maybe all that matters is this. Somewhere a Doctor needs to come here, even though it doesn't change anything at all. And maybe now the Doctor's not strong enough; maybe nobody is. But if there was a monster that no one would ever acknowledge… then you'd have to fight it, wouldn't you?" She nodded at the wall. "She taught me that, when I was her."
She was looking at the woman in the wall with a stare like the man in the book, like she was looking at her home long after it had been destroyed.
"We're shadows," she said. "And we fell off a much bigger story. But that doesn't mean"—
The old woman wasn't getting any of this, the Doctor saw. She was listening out of politeness, like she might to one of her grandchildren.
"People don't understand what a shadow is," said the Doctor. "It's not ever opposed to the light. It needs it, it's built by it. A shadow's only cast when the darkness hasn't come. It's not the reverse of hope, is fear. It's what some people need if there's to be any hope left at all."
The old woman looked confused.
"I do have a question, if that's alright," she said.
The Doctor smiled. "Try me."
"If she's you, and you're another you, and both of you are from somewhere that's different from here," she said, "then where is this? And what am I?"
The Doctor looked up to the dome that hung still in the sky.
"You're doomed," she said sadly. "This whole planet is. There's no way to stop it, not now."
"Oh. But I don't feel doomed."
"No. People don't, do they? The planet goes on for millions of years without you; there's a missile that can kill a city that's aimed right at your head. It's not enough to know a thing is true, is it? If you don't feel it."
"You're telling me I'm about to die," said the old woman. "Although I am getting on, I suppose. Maybe I was going to anyway."
"It won't be long now, I'm afraid," said the Doctor, looking up at the laser pointing down. "It's almost eight 'o clock."
"Do you know that bit in the book?" said the old woman suddenly. "A woman works it all out; sees there is a way she can save everyone. But by the time she does, it's already far too late."
The black eye of the laser could have been staring at them, bleak like the barrel of a Dalek's gun.
"I know the book very well," said the Doctor. "I sent in some of the sound effects. And I know the universe might do what we'd all rather wish that it can't. But we still have to hope, don't we? That this isn't that kind of a story."
"Perhaps that's true," said the old woman. "It did all look hopeless way back then. None of us really thought any of it would work out for the best. And now"—
"You're alone in an alleyway, eating shadows," said the Doctor.
"I lived to be old. It's more than I ever expected."
"Yes," said the Doctor as she looked at the pressing hands. "And what you escaped is worse than you'll now ever know."
"Oh?" said the old woman. "That's nice, then."
"It's something," said the Doctor. "There's always a light in the darkness."
The dome hung low in the sky, great as the silence.
"It's late," she said. "Best be getting on. Sorry if you've thought I'm a little bit strange. I've not been myself today."
The old woman blinked, and there was silence. The odd person in the alley had gone away, and after a while the one in the wall was gone, too.
"I've no idea what any of that meant," she said to herself, when she was finally sure she was alone.