The two of them stood silently for a while after that, both looking up at the Porter’s frozen form.
“You must understand,” said the other Doctor to her future self. “This isn’t what I’d hoped for. Or even anticipated. I’d wanted there to be another way.”
“Than killing him in cold blood?” said the Doctor.
“There was warmth in it, the same as cold. Or weren’t you listening to the poem just back then?”
“I know it,” said the Doctor. “Robert Frost.”
“It’s a funny coincidence, isn’t it?” said her other self. “Frost by name, Frost by nature.”
“Oh yeah,” said the Doctor sullenly. “It’s hilarious.”
She looked around at the wreckage, and at the ice.
“Frost,” she said. “The poet. Whatever happens here, he dies not long from now. It doesn’t matter much about the ending, not for him. Like he said, however it happens. Some things can’t ever be changed.”
She stared out of the window, away from the devastation. Out at the world outside, where there were trees.
“Two roads diverged in a yellow wood,” she said. “And sorry I could not travel both, and be one traveler, long I stood”—
—she trailed off, and sighed.
“I can’t let you do this,” she said.
Her other self laughed, in shock as well as bemusement.
“Let me?” that other self now said. “Good Lord, dear, I’m”—
“I know. You’re me.”
“Then I don’t see why you’d want to stop me,” the other Doctor said. Her tone had changed, the Doctor noticed. Now there was only the cold.
“I left you a message in the Matrix,” that other Doctor went on. “Whatever they’ve done to you, it changes nothing. You are still the Doctor. And somewhere like this?”
She gave a grim smile.
”It’s where we’re needed most.”
“I don’t disagree with that,” said the Doctor softly.
The other Doctor threw up her hands, ready to get theatrical.
“The Planet Earth!” she said, sweeping her arms around to draw it all in. “Surviving this crisis, and everything time throws at it afterwards. It’s maybe the biggest anomaly we know of; blown my chameleon circuit clean apart. Any TARDIS landing here might get stuck in one form for a while.”
“And then things would look the same,” said the Doctor. “On the surface.”
“I got your message,” she said. “I think. It was like you said: whatever happened, I was still the Doctor. But maybe I got the wrong end of the stick”—
Her other self’s eyes narrowed.
“I didn’t think I needed to explain,” her other mouth said.
“Try me,” said the Doctor, her eyes now narrowing too.
“They say that time heals all wounds,” said her other self. “But there are so many wounds in time. When I –when we– first arrived in this universe, it was sick with contradictions. It needed healing. It needed”—
“Yeah, yeah,” said the Doctor. “I get it.”
“But that’s the thing. I thought you did. I know what you’ve done here, as you’ve travelled through this planet’s history. People have begged you to change how it all turned out; I’ve seen it! At the massacres in France, in Pompeii. Why would 1962 be any different?”
“Now it’s a whole world,” said the Doctor.
“A world like many others no one saved. They’ll say the end was inevitable, in the ruins of this city. And like on so many other planets? They’ll be right.”
“You know I’ve seen a future that disagrees,” the Doctor replied. “Where humanity spreads out across the stars.”
The other Doctor scoffed.
“Oh, cut it out,” she said. “I know humans. I’ve been one! There’s nothing remarkable about them. You must know that. A primate civilisation, highly tribal. Smart enough to build weapons that can annihilate them; thick enough to make sure that they’ll be used. It’s happened across the universe, a million times. You know that it should happen here as well.”
“Should’s doing a lot of work in that sentence,” said the Doctor coldly.
“No it’s not. Like I said; it’s the logic that you’ve always used. I don’t see why you’d think it’s different here. Unless”—
The other Doctor’s eyes widened in horror.
“Oh no,” she said. “You’ve fallen in love!”
The Doctor knew she was blushing, despite herself.
“No I haven’t,” she said.
“Yes you have! And it’s a forbidden love”—
The Doctor looked very awkward indeed.
—“the love of one special place, at a special time.”
“Oh!” said the Doctor. “Yeah. That.”
Her other self shook her head.
“Whatever we do, you have to understand,” she said. “We can’t ever be guided by love. I loved the Porter. But that’s what he never understood.”
“He was fighting to save this world,” said the Doctor. “You told me what he was doing here was immoral.”
“And I stand by it. Maybe I do bend some of the rules. But never the ones that really matter.”
“And you don’t see a problem with that? When nuclear annihilation’s the price?”
“Of course I don’t. We stand for the universe; our morality has to be universal. We can’t start making exceptions. Gravity doesn’t get to decide who falls. Neither can we. Otherwise”—
She frowned. The Doctor could see the frustration in the eyes of her earlier self. Like this was something she shouldn’t even have to explain to a child.
“Otherwise what’s good or bad depends on whoever we meet,” the other Doctor said. “We’ll treat people better because they’re in front of our face; not think about the ones we never see. Maybe that’s how they do things here, on this world. But the Doctor has to be better.”
“You’re a killer and you think you can talk about universal morals,” said the Doctor.
“Because I can’t ever choose who’s gettting killed. If I decided who got to live and die? I’d be a monster”—
The Doctor glowered.
“Don’t you dare make nuclear annihilation sound like it’s noble,” she said.
Her other self sighed, slumping into the folds of her coat. The weight of worlds seemed to literally press down upon her shoulders.
“Of course I have compassion,” she said, “But I can’t choose some people over others. Preventing history’s path because I don’t like the outcome— do I have the right? Out of this catastrophe might come some good, you know. Maybe even for them.”
The Doctor’s eyes widened in horror.
“How can you possibly say that?” she said.
“Look at where we are. A doctor doesn’t prolong a patient’s pain. It’s not about delaying the inevitable.”
”That’s the only thing that being a doctor’s about.”
Her other self didn’t respond at first, as she stared down her nose at the Doctor. When she next spoke she did it softly, gently. Like she was addressing a patient about to get a terrible diagnosis.
“Can’t you feel it?” she said. “What’s happened to space and time? Because of the end that failed to happen here. Can’t you taste the strain?”
The Doctor stuck her tongue out and tentatively wiggled it around.
“Only the air,” she said. “Still cold as death.”
“Then you should know,” her other self said, “that it’s splintering, Doctor. The past and the future, they’re not what they previously were. Orphan planets in possible timelines! You know that it should be impossible. But it isn’t; not anymore. The pressure that’s building here could take down the universe.”
“And the people who come from here might save it,” said the Doctor.
“How likely does that seem? When it hasn’t happened anywhere else?”
“They have something that everywhere else doesn’t have. Hope. And love. And believe me, Doctor. Love always wins in the end.”
The other Doctor looked at her future self like she might look at a person without a brain. It had gone further than pity, now. Now she was actually afraid.
”What have they done to you?” she said. “I knew that they were planning something. But this?”
“I’m you, just like you said! Nothing’s changed, I am the Doctor”—
“Doctor who?! You’re everything I swore never to be! Good grief. What have I become?”
She looked her future self right in the eyes.
“What do you know about the laws of time?” she said. “What are you still able to feel?”
The Doctor frowned.
“The same as what any Time Lord can,” she said. “The threads of the timelines knitting together. Our sense of how everything’s balanced”—
Her other self shook her head.
“Then it’s as I feared,” she said. “You don’t understand anything at all. The Time Lords follow the laws that I laid down. But only something from beyond the Boundary could really understand their necessity.”
“And maybe only someone from this side of it could understand why you need to be stopped.”
The Doctor’s other self drew up to her full height, her spine as straight as a policeman’s, her eyes burning furious as justice.
“If that’s what you think?” she said. “Then the Doctor is already dead. You’re standing against morality itself. And I don’t make any exceptions, for people who make that choice.”
Fire crackled between her fingers once again.
“Not even for me,” she said.
Her other self was a good woman, the Doctor saw. Perhaps she always would be, whoever she happened to be. And in her recent lives she’d hoped that would make it better, for the doomed lives she’d left in her wake. But now she was in their place, and now she knew: somehow, the goodness made it worse.
“I’m sorry,” her other self said. “I’m so sorry.”
That didn’t help as much as she’d thought it did, either.