The cloth-bound figure hissed at Yaz, its metal claws outstretched. And as it did Yaz felt the fight going out of her, her body now telling her it was time to just give up and die. Claws might not be the worst way to go, after all. They might be less painful than dissolving to nothing at all.

The figure wasn't killing her, though. It didn't even seem to be trying. It just kept repeating the same phrase over and over, its voice harsh below the scream of the birds.

"What is this? What is this? What is this?" it cried, gesturing to its torso with its claws. Was it indicating itself, or the question mark on its chest? It was hard to tell.

Yaz decided to humour it; answer its question. It was an Ergon; the Doctor's before it hatched. But the Doctor had said a creature like it once went by another name. She'd had a cloth man like this before, and her friends had called it a Watcher. And it would appear when you knew you were in danger, when you wanted above anything to survive—

Maybe it was just her imagination, but as she thought that she felt the figure was staring straight at her.

"What is this? What is this? What is this?" it screeched.

It paused.

"And what are you?"

Yaz stared at it, trying not to sound scared.

"I'm… I'm a person," she said. "A human. The Doctor's friend?"

The figure looked disapproving as Yaz felt an odd pain in her legs.

"I'm usually made out of matter?" she said, desperately.

The cloth man's voice grew even louder and angrier.

"What is this?" it cried. "What are you? What is this? What are you?"

Despite everything, Yaz felt herself getting frustrated. This wasn't how you spoke to people. Not in real life. It was like some stupid children's story where some creature would set them a puzzle. Or a mystery story on TV where they all had to solve it at the end—

She froze.

They didn't all solve it, though? Did they?

"What are you?"

Yaz was a police officer. An investigator. And a great big question mark—

"What is this?"

—was a clue.

"Oh, come on," she said, exasperated.

But another part of her had switched on, was whirring into gear. Put it together, it said. So this is a case, just like any other.

She knew what they'd said before their first time out on duty. They'd be in places they wouldn't believe, see things you never did on TV. So what if she didn't expect to have to do police work out here? No wonder they put you on paperwork if you weren't able to deal with the unexpected.

"What is this? What is this? What is this?"

It was the Doctor's Ergon before it had broken free—

Establish the facts, said the voice in her head. Eliminate what you'd assumed.

She'd never actually seen it hatch. Had she? She'd seen the Watcher and the Doctor's bird, assumed they were one and the same. But what if they weren't? The Doctor had said her Watcher had come to Yaz because of the bond between them. But what if she'd been wrong?

What if the Watcher had never actually belonged to the Doctor at all?

"What is this?"

Because she hadn't called for the Doctor, before it came here. She'd wished for anyone who might be able to save her—

"What are you?"

—Yaz stuff, Doctor stuff. There had to be a line. But the Doctor had said that, and she'd been making up rules all along—

What was the point of a Police Box if you never got to do any policing?

—the Doctor was older than she'd known, but the box was even older than the Doctor—

"That's your problem," Omega was shouting up above her. "You always think that everything's about you!"

Yaz looked right at the Watcher.

Her Watcher.

And she took a very deep breath.

"Yasmin Khan," she said. "You are under arrest for breaking into the Sheffield Headquarters of Hallamshire police."

The Watcher looked back at her, impassively.

"You do not have to say anything," she went on. "But, it may harm your defence if you do not mention when questioned something which you later rely on in court. Anything you do say may be given in evidence. Including 'What is this?'" she added, unprofessionally.

For a moment the Watcher stared, saying nothing at all.

And then it spoke in her voice, as Yaz. Not the voice she heard in her head— the one on tape recorders and videos, which always made her cringe. But it was still different to that as well, very slightly. It was confident. It seemed assured.

"I had a right to be there," Yaz heard that other her say. "I was undercover. Helping an officer in need."

And under the cloth that covered her face, she could see as she started to smile—

—and then the bandages were a mummy unraveling, falling away to reveal the Yaz underneath. But this Yaz looked taller than she did. Happier. More confident. Yaz was the kind of person who'd always cringe when she saw herself in photos. She knew she never would if she was able to hold herself like that.

She was in full uniform, as well. A police officer with a police box, ready to save the day. There'd been someone out there who was able to help her, after all. Herself. But she'd had to be ready.

The Ergons had noticed what was happening below them, now, and so had the two people who were bound to them. The appearance of the other Yaz had seemed to shock the Doctor and Omega out of their anger. Fleetingly, they were able to be themselves again.

"Yaz," said the Doctor through a wince of awful pain. "It's me; really me. But I won't be able to hold off the rage for long. That other you is a Watcher; same as mine. When you want it enough, they're the person you're going to be."

"I'm not her!" said Yaz. "She looks like she knows what she's doing. I wasn't even needed in the lockdown! I was on paperwork."

"Maybe," said the Doctor, frowning. "I thought it was impossible for a human to summon an Ergon"—

Omega now spoke as well, real strain audible in his voice.

"And once it was impossible for someone to discover time travel," he said. "Many things can never happen, until they do."

"Yaz isn't the sort of person who does that," said the Doctor.

"Then maybe it's past the time you allow her to be," said Omega.

The Doctor looked shocked at that, and for a second Yaz feared she'd be lost to her fury again. But instead she was quiet, silent. From the ground Yaz saw her give a very slight nod.

"The things we hold inside," the Doctor said to her. "What we're holding back. They're not the worst of us, not always. Your Ergon's not a monster same as ours. That woman there, Yaz, she is already you. You just need to go to her. To allow her to be."

Yaz laughed, and looked over to the other her. She was everything she'd always dreamed of being. But to live your life as your dream? Even after travelling in time and space, that seemed uncomfortable.

"Will it hurt?" she said. "Becoming her?"

The Doctor looked uncomfortable.

"Yes," she said, and it was the first time Yaz knew for sure that she'd been honest.

Something flashed across the Doctor's face, and she was lost. Her and Omega were screaming at each other again, once again swallowed by rage. But that was okay, perhaps. Maybe they'd both done enough.

Yaz looked over at the other her, who smiled back.

You're an authority figure when they see you, she remembered the lecture saying. They see the badge; the uniform. At first, it'll feel like pretending. But you have to play pretend before it's real.

Maybe the Doctor had felt like this, a long, long time ago. When she was the first of her. The first time she saved a world.

Yaz walked over to her Watcher, and held out her hand—

—and lost focus, though only for a second. But when she recovered she was in her uniform, could feel her whole posture as different and could see what she now had to do. And the Doctor had been wrong, because none of it had hurt at all.

It would be wrong to say that she'd made a choice. It had taken her a long time, to get to the place this was possible. But now it was, and now she let it be true. Now she became the person she wanted to be.

"Right," she said to Omega and the Doctor. "Get down here."

She glared at them.

"Both of you," she said. "You're coming with me."