Author's Note: So, this went off-prompt (I was supposed to write about coffee, but it became a minor detail). It's supposed to take place sometime during Season 11 or 12, but it's before The Haunting of Villa Diodati. It doesn't fit perfectly with cannon, but *shrug*. I'd love any suggestions for a better title.

Disclaimer: I don't own Doctor Who.

It was six thirty-nine in the morning. Yaz sat hunched over her coffee cup, eyes half closed. It was still dark out, and she had been forced to use her phone's flashlight to find her way out of the house. She had spent last night buried in mountains of paperwork and it wasn't even half done yet.

"You look tired," Ryan said from across the table.

"'course I'm tired," Yaz told him.

Ryan sighed. "It's…it's strange, you know? I thought I'd like a bit of peace and quiet after all of this. But…"

"Everything seems too quiet," Yaz said. "Everyone's half asleep."

"You look half asleep."

Yaz laughed quietly, but her expression fell a moment afterwards. "Yeah, I do, don't I? It's the paperwork. I can't seem to stay out of trouble. Maybe I think I'll see her again. You know the Doctor. Explosions, and she comes running. But it's just normal people. Why would she be there? She left us."

"She said she had to," Ryan said quietly.

"She dropped us off in the middle of Sheffield and left. No explanation. No warning. Just left us behind. 'I have to' isn't enough. We were friends for years. Family, she said. I thought we…I thought she cared about us."

"The Doctor was panicking. Yeah, she went about it wrong, but she was scared."

"Scared of what?" Yaz snorted. "She didn't tell us anything." She took a sip of her coffee.

"I don't know," Ryan said. He thanked the teenager who brought him a coffee of his own. The shop was nearly deserted at this hour—there was only a man in a business suit reading a newspaper in one corner and senior couple quietly discussing yarn prices. "But she'd never leave us without a reason."

"How do you know that?" Yaz asked. "We know nothing about the Doctor. Travelled with her for years. But we didn't even know her home planet until her past caught up with her. She told us that we don't know her. She was right."

"So, you aren't searching for her?" Ryan asked.

"Of course I'm searching for her!" Yaz nearly shouted. The businessman glared over at the table and muttered something. Yaz didn't even have the energy to roll her eyes. She slumped down in her chair, taking another sip of coffee. "I've been on every one of Dad's conspiracy theory servers."

"And?"

Yaz shook her head. "It's impossible to sort out the noise from the actual information. There are tons of 'doctor' theories, but no sightings of this one within the relevant time period. I had to leave after this one creep started asking me weird questions about her, like they knew that I knew her. I did find a photo of the time with the frog, though." Ryan laughed and Yaz gave a weak smile.

The door creaked open, but Yaz didn't look up. "Maybe she's in hiding," Ryan said. "Lying low for a while."

"Yeah," Yaz said, still looking at her coffee. "Hiding from us."

"Look, I'm angry at her too. But I know she must have had her reasons. She cared about us, and that's why she had to leave us here."

Yaz looked up at him. Yaz looked past him.

The Doctor had just watched into the shop. And it was definitely the Doctor. But instead of her normal costume she wore jeans and a T-shirt, and her eyes were all wrong.

"What are you doing here?" Yaz hadn't realized that she had stood up.

"Well," the Doctor said cheerfully, "I discovered that I required some caffeine and had a feeling that this was the right place."

"How…how can you just, just waltz in here, smiles and rainbows?" Yaz asked.

"Smiles are beneficial to your health," the Doctor said.

"You left," Ryan said.

The Doctor paused. "I've left many places. Which one are you talking about?"

"You left us," Yaz said.

"I think you're mistaken. I don't know you."

"You forgot us already?"

"What are your names?" The Doctor asked Yaz.

"Stop messing around," Ryan said. "Just tell us why you had to go."

"I don't know what you're talking about. Who are you?"

Yaz squinted at her. She wasn't hallucinating, since Ryan saw her too. It could be something having to do with aliens…but why would they make her think the Doctor didn't know her? It wasn't like this was even her worst fear or anything, it was just wrong. "Yaz and Ryan. Graham said it was too early to get out of bed."

The Doctor shook her head. "I haven't met you." She held out a hand. "Joan Smith."

Yaz raised an eyebrow. "Joan Smith."

"That's the name."

"But…you're the Doctor," Ryan said.

"Always wanted to get a medical degree…unfortunately I don't seem to have one. I'm a teacher." Yaz stared. The Doctor didn't seem to recognize her at all. And her eyes…they were bright. Happy. The Doctor hadn't been happy since before the Kasaavin.

"Seriously, though, Joan Smith?" Ryan asked.

"Is there a problem with my name?" The Doctor—no, Joan—bristled.

"It's kind of, well…"

"Sorry," Yaz said, cutting Ryan off. "We thought you were someone we knew. You look just like her."

"Mustn't have been a very nice person," Joan said. "Seeing how upset you were with her."

"She was…amazing," Yaz said. "But she left, and we don't know why. Didn't even say a word."

"I'm sorry," Joan said. "Must've been hard."

"Er, would you like something?" The teenager behind the counter asked nervously.

Joan ordered a chocolate Frappuccino. Yaz stared. Ryan shook his head.

"So," Joan said, sitting down in the table next to them. "Yaz and Ryan. Oh, I'm awful at small talk, you go ahead."

Yaz laughed. It felt kind of nice, laughing. "Where are you from?"

"Oh, I live in Sheffield."

"Haven't seen you around," Ryan said. "I come here for coffee a lot."

Joan shrugged. "I had a feeling I'd like to try something new today. Thought this place might be a good idea."

"I'm a police officer," Yaz said. Joan was so similar to the Doctor, it was uncanny. And there was her name—Joan Smith. The blandest of bland pseudonyms. This wasn't the Doctor, but Yaz was certain that Joan wasn't all she seemed. She frowned to herself. The coffee was almost done; she'd have to order more. Oh, well, she could use it anyway.

"You seem like you'd make a good one," Joan said.

"Thanks," Yaz said. She looked over at Ryan, who was focusing on his coffee. "So, you're certain you never heard of the Doctor?"

Joan shook her head. "Sorry. But I'm sure you'll find her eventually."

"I've tried everything. She doesn't want to be found," Yaz said. "She left me—left us—on purpose."

"Then she'll come back as soon as she can. She'd have to be stupid not to." Joan paused. "What I mean is, you obviously really care about her. Good friends are hard to find."

"'She had her reasons' isn't enough," Yaz said. "She could have let us help her. Could've told us where she was going. At the very least she could have told us why she had to go."

"Maybe she couldn't," Ryan said, finally looking up from his coffee. Yaz looked away, planning to get more coffee, but the teenager wasn't behind the counter. She looked back at Ryan.

"Yeah, maybe she was a spy or something," Joan said, her eyes sparkling.

Yaz laughed again, then caught herself. She shouldn't be laughing at six forty-five in the morning with the Doctor off who knows where. Probably getting herself killed. "Close," she muttered. "Alien."

"Really?" Joan asked.

"Really."

"Nope, you're pulling my leg," Joan said.

"Definitely an alien," Ryan said.

Joan looked at her cellphone. "Sorry, I have to go. My school starts soon."

She picked up her Styrofoam cup. Yaz grabbed a napkin and scribbled down her name and phone number. "Yasmin Khan," she said. "Call me sometime."

Joan smiled, tucking the napkin into her pocket and leaving.

"You just asked the spitting image of the Doctor to 'call you sometime'," Ryan said.

"Shut up," Yaz told him. "I'm gathering information. Investigating. Joan Smith? She's…she's not the Doctor, but she's really, really close. I should've gotten her pulse, seen if she had two hearts."

"Yes, you should've held hands with her," Ryan said.

"No really, shut up." Yaz told him. She looked at her empty coffee cup. No excuse to stay now, and it didn't seem worth ordering another one with Joan gone. "I have to get to the station now."

"Good luck with the paperwork," Ryan said. Yaz grimaced.

Something exploded.

Or, rather, there was the sound of an explosion behind the shop. The businessman sat straight up, eyes alarmed while the senior couple started immediately chattering. "Everybody keep calm," Yaz said. "I'm with the police. I'll go see what's happening. You should stay in here and don't go outside."

"Wait," Ryan said. "Aren't you supposed to be on parking disputes?"

Yaz raised an eyebrow at him. "You coming or not?"

"I'm not filling out any paperwork."

"I'll add it to my queue," Yaz said, rushing out the door.

She ran down the street, turning a corner and ending up in an alleyway. Joan was there, her face covered in soot and hair sticking out at odd angles. And in front of her was the teenager from the coffee shop, mouth curled into a sneer and eyes alight with malice. Behind him, the shadows seemed to form a whirling tornado, winds whipping at his hair.

Alien. Yaz smiled.

"…but you're blank, aren't you?" He was saying. "And you're scared of it. Smart enough to realize something's wrong, terrified to test your hypothesis. I can see…it all."

"I—" Joan stammered, leaning on one of the walls. "I don't understand."

"Get away from the civilian," Yaz said. "By the order of the…erm, Judoon. Yep." She thought back to their adventure with the Judoon, still fresh in her mind. "Imperial Regulator Yasmin Khan here."

"You are human," the alien said. "And you are scared. You've got to keep faking it, don't you? Fake till you make it. Stand tall and pretend you're confident. Speak loudly and pretend you're knowledgeable. Smile and pretend you're happy—rather like your friend over there. But you like this, the thrill of fighting. Nearly dying. It's why you're not going to back down. I'm afraid I'll have to kill you."

"You can try," Yaz corrects. "But I wouldn't suggest it. I'm rather hard to kill. More importantly, I'm an…imperial regulator. So. There will be…diplomatic repercussions if you interfere with my imperial regulation."

"You're lying. You're also very, very bad at it," said the alien. Yaz had to admit that he had a point.

"Just tell us what you want. We can negotiate. Right Ryan?"

"Er, yeah. Negotiation. That's a thing that we can do. We speak on behalf of the Earthlings. What do you want?"

"I require the secret."

"There are quite a lot of secrets in the world, you know," Joan said, finally peeling herself off the wall. "Apparently aliens are one of them. Which one are you after?"

"The Time Lords. Where are they?"

"Ah." Joan said. "No idea what you're talking about." She turned to Yaz and Ryan. "Do you have any idea what he's jabbering on about?"

"Er, no," Yaz said.

"Yeah, can't help you mate," Ryan agreed.

"Oh, you know," the alien said. "But not enough. I require the Doctor. And the Doctor is here."

"Someone's already made that mistake today," Joan said. "Hi, Joan Smith here. Teacher. Not a doctor. Unfortunately."

"She's not the Doctor."

"No, she is not," the alien said. "The Doctor's mind is missing, and it holds the secret. I require the secret."

"I can't help you," Yaz told him. "I don't know where she is, and if I did, I definitely wouldn't help you."

"Joan Smith."

"Yeah, we've established that," Joan said. "Now, you're going to go away and leave us alone. Take your creepy shadows elsewhere."

"Strange," the alien said. "It doesn't work." He turned to Yaz. "Yazmin Khan." Yaz suddenly felt as if her mind was on fire. Numbers ran through it—they were written in a strange script but Yaz knew in every fiber of her being that they were numbers. Equation after equation filled her head, pushing out all other thought.

"Yaz?" Ryan asked, and his voice became numbers in her head. Amplitude, frequency, phase shift. Up, down, up down. Sound waves.

"Give me the necklace," the alien said. His words were numbers in his head, 1 and 26 and impulses through muscles and ones and zeroes, on and off. They were numbers. Equations. Yaz's equations. Yaz stepped forwards towards Joan.

"Yaz, what are you doing?" Ryan asked. Disregard. Delete. Extraneous solutions.

A golden chain sparkled around Joan's neck. The necklace. Yaz had to get the necklace. That was the missing variable.

"Give it to me," she heard herself say.

"I don't understand," Joan said.

Yaz stepped forwards again, felt herself reaching for the necklace.

"Yasmin Khan, whatever it's doing to you, you need to fight it," Joan said. "You can do it. You're strong enough."

"You're not strong enough to do anything. Not even enough for the Doctor to stay. No wonder she left. You have your orders, officer Khan. They're all you're good for." Yaz was numbers. Yaz didn't exist.

She reached out to grab the necklace. Joan punched her, but it didn't hurt. Shadows swirled around her, absorbing Joan's hand, coating it with darkness. Yaz grabbed the necklace, watched the numbers surrounding it. Thousands of numbers. Energy filling the center which wouldn't open, shouldn't open, couldn't open.

Yaz could open it.

Two mouths twisted into smiles, but only one person was the one smiling. It wasn't Yaz.

"Good. Now bring it to me."

Yaz stepped forwards.

"Yaz, you can fight it!" Ryan shouted, grabbing her by the shoulder. She punched him and he fell. Yaz watched his equations, watched him fall in her head. He wouldn't die, wouldn't even get a concussion. Pity.

"Give that back!" Joan rushed forwards. "The necklace was my grandma's, you can't open it, it's useless, just give it back." Yaz tried to hit her, felt her arm raising. Joan grabbed her. "Yaz, come on. You need to fight…whatever the alien is doing to you, you need to stop him. You need to save the Doctor."

"I—" Yaz said (not felt herself say, said). One letter in the middle of numbers, polluting the equations. It was wrong. Wrong, wrong, wrong. And also right.

The numbers were wrong. They failed to account for so many variables. Their solutions were off. Yaz didn't have to listen to the numbers.

"You can do it!" Joan said. "You're strong."

"You're weak." Yaz watched in horror as the alien twisted his hands. The shadows around him formed into two spears of darkness, which he sent flying through the air into Joan's chest. She gasped in pain, falling against the wall of the alleyway.

"Now bring me the necklace," said the alien. "Bring me the Doctor."

Yaz froze, horrified. In her mind, the numbers stopped.

And then Yaz started, the numbers gone. She could finally think, her mind clear. Yaz turned around to face the alien. "Who are you?" She asked, struggling to keep her voice level. Behind her, Joan was dying and Ryan was lying unconscious on the ground. "And what do you want?"

"I am Zero. Now give me the necklace."

"Why don't you get it yourself?" Yaz asked defiantly, holding it behind her back.

"It's far easier to use fools such as yourself, Yasmin Khan."

Yaz felt the numbers push at her. But inside her mind, she felt something else rising up. Joan—who might also be the Doctor—was dying. Joan, who had ordered a chocolate Frappuccino and suggested that the Doctor was a spy. Doctor or not, Joan was her friend. And she was dying. There wasn't any room for the numbers in Yaz's head.

It might be too late. But whatever was inside the necklace, the alien wanted it. And he couldn't get it. The Doctor's life depended on it, if she wasn't already there, dying behind her. Yaz would not let him get to the necklace.

She could run. But where would she go? Ryan needed her help, needed medical attention.

So she had to fight. Yasmin Khan was going to fight if it killed her, and it probably would.

"No," Yaz said. "I'm not easy to control. Now. You get others to do your dirty work for you, whether they're shadows or people you've done your number mind thing to. Which means, you can't do it yourself. Why?" Yaz slowly took out her cellphone. She wasn't sure who she would call. Maybe her family. Try texting the Doctor, not that it would do any good. Except—the alien, Zero, used shadows. And Yaz's cellphone had a light.

"Give it to me, or you'll die just like her," Zero ordered.

"No," Yaz said, turning on her iPhone's flashlight in her hands.

Zero sneered, sending a spear of darkness towards her. Yaz held up her light and the tentacle writhed in pain. Zero, however, seemed unaffected, if slightly worried. Yaz stepped forward. The alien flinched.

"When you gave me my coffee," Yaz said, taking another step, "you wore gloves. I didn't notice it; too tired, too focused on my own problems. You have your servants do your dirty work for you. If you needed the necklace, why didn't you get it yourself? You can't."

"You don't know what you're talking about," Zero said.

"You can read my mind. You know exactly what I'm thinking." Yaz took another step. She was only a few feet away. "You know what I'm going to do. I'm going to stop you, and you know I can." Yaz lunged forwards, catching Zero's arm as he tried to run. It began to disintegrate in her hands, turning to black ash. Yaz punched him in the face and watched as his head caved in, watched as he became a pile of ash on the ground.

"Brilliant." Yaz turned around. Joan had slid down to the ground. Inky blackness was spilling from where she had been stabbed, but there wasn't any blood. Yaz knew first aid—she had to, as a police officer—but she had no idea how to help.

"Joan," Yaz said, kneeling down next to her.

Joan was smiling, somehow. She was dying, and she was smiling. "That was…" She gasped in pain. "Brilliant, Yaz."

"We need to, we need to try to stop the bleeding," Yaz stammered.

"I don't need a medical degree to know this isn't blood," Joan said, looking down at herself. "This…this Doctor. I think I'm her. Or was her."

Yaz could hear sirens in the distance. "I'm sorry."

"Didn't do anything wrong," Joan whispered. "I don't think I'm going to be able to call you."

Yaz felt as if she should be crying, but the tears just wouldn't come. "It's okay. You're not going to die."

Joan ignored this. "The necklace."

"Here," Yaz said, holding it out to her.

"I think your friend's in here. Pandora's box. I taught Greek myths, you know. Not for very long. I only just moved here a month ago. Think I've only been alive a month."

"I'm sorry," Yaz said again. "You didn't deserve to be caught up in this."

"I'm finally going to earn my medical degree."

"That's right, you're going to live," Yaz said. "And then…we'll figure it out."

"No," Joan said. She reached for the necklace but her hand fell. Her eyes were half closed. "No, the Doctor's going to live. The necklace."

"I don't know how to fix this," Yaz admitted. "I don't know what to do."

Joan's face pulled into a mischievous smile. "I think—I think you're supposed to open it." Yaz put the necklace in Joan's hand. "Always been stuck closed," Joan said, her voice hoarse. "Except I never checked. Silly me."

Yaz undid the clasp, and together, they opened the locket. Out of it spilled golden energy, forming around Joan. The darkness flew from her chest and Joan's eyes drifted shut. "Joan?" Yaz asked. No response. "Doctor. Doctor! This was supposed to fix you…you're, you're supposed to be alive!" Yaz felt for the Doctor's pulse, but it wasn't there. "Please!" She placed her head on the Doctor's chest, desperately hoping to hear something.

Nothing.

And then…

A faint thrumming sound. A double heartbeat.

The Doctor's eyes opened. "How come it took turning into a human to get my friend's phone number?" She asked, sitting up.

Yaz looked behind her. The sirens had stopped and the police stood behind them outside of their cars. "Right. This is going to be difficult to explain."

"You could have told us what you'd be doing," Yaz said. "We'd have helped you."

"It was too risky. The creature, Zero, could see everything you were thinking. No one could know."

"I still can't believe you called in UNIT to talk to the police chief," Ryan said. "I mean, his face was just…"

"Unfortunately, I don't think that he'll remember much of this once they're done debriefing him. Fortunately, Yaz is going to keep her job."

"Not long, if I don't finish my paperwork," Yaz said.

"Oh," the Doctor frowned. "I was going to take you to the Crystal Falls on the planet Isbethimal."

"Well," Yaz smiled. "It is a time machine.