Clara's lungs were filled with smoke. She could barely see, much less breathe, but the argument she had been having with the Doctor prior to the explosion continued, as heated as ever.

"I thought you said that other aliens couldn't time travel. Always one of your big points—'Oh, look at me, so special with my unique time travel technology. What the hell is this, then?"

The Doctor's hands were flying a million miles an hour, dancing over buttons and levers on the control board as if they had a mind of their own. "Okay!" He called over the sound of the TARDIS' emergency sirens, "Maybe I over exaggerated that part just a bit. But I didn't realize these ones were hostile! I didn't think it mattered!"

"Well yeah, it didn't matter," Clara snapped at him, "Until you had to go and make them angry!" The events of the past few hours were all a bit of a blur to Clara—one moment it had been a peaceful trip to a once-in-a-lifetime festival on a different planet millions of lightyears from Earth, and then the next thing she knew, they were on the run.

The TARDIS lurched to the side, throwing Clara against the metal railings. Her head slammed into the top bar, and she sunk to the ground, clutching at it with one hand and clinging desperately to the rails with the other. Her vision was tinged with red.

"We've been hit!" The Doctor yelled, dashing around to the other side of the console board and out of Clara's sight. "We don't have much time!"

Clara struggled to her feet, grabbing at anything she could use to keep herself steady in the constant lurching of the ship. "What are you going to do?" She asked, then broke down into a fit of coughing as she inhaled another lungful of smoke.

"Well, you know what they say—Desperate times call for desperate measures!" There was a high-pitched screech and the floor suddenly steadied. Some of the smoke cleared, and Clara gasped for air and stumbled across the central platform to stand next to the Doctor.

"Did we get away?" She asked, her voice hoarse. The alarm sirens had faded, but the red lights were still pulsing silently.

"Weeeeell…" The Doctor grimaced. "Unfortunately, no. They're much harder to evade than that. I've just engaged the high-power shields, which hide us from their sensors for the time being, and stabilized the gravity in here."

"I'm sensing a huge 'but' coming up," Clara said nervously.

The Time Lord straightened his charred bow tie with an air of haughtiness. "For all you know, Clara Oswald," He began, "I could have just saved our lives with no 'buts' involved! You don't give me enough credit, you know. A thousand years of time and space, I know this thing like the back of my hand." He held up one hand and wiggled the fingers at her, as if to prove a point.

The floor began to quake subtly. Clara crossed her arms and glared up at the Doctor. His eyes flickered from the lever he was still holding with one hand back to his irate companion, and finally cracked. "Okay, okay!" He said, raising both hands in defeat. "There's most definitely a 'but' in this situation. With the high-power shields on, they can't see us, but it also drains the power at a rate of…" He trailed off and glanced down at a dial on the console. His hands dropped and he instantly turned away from Clara, turning to fiddle with the instruments. "No, no, no," He muttered under his breath. "No, no, no, no, NO!" He slammed his hands against the console. "That's just no good!" He sucked in a deep breath and ran his hands through his hair, his eyes wide with panic.

"Doctor?" Clara asked tentatively. "What's going on?"

"We're almost out of power," He said grimly, "And the shields are going to falter in about two minutes."

"Two minutes?!"

"If we're lucky." The Doctor turned back to Clara and fixed her with one of the most intense stares she had ever seen him give. His hands gripped her shoulders. "Listen, Clara," He said softly. "I didn't want to do this. I really didn't, but there's no other choice. I'm sorry. I'm so… Sorry."

Clara opened her mouth to respond, but found herself cut off as he pulled her into a sudden hug, his arms wrapped around her with bone-crushing strength. "What's going on?" She managed, trying to grab onto him as he let go of her.

His gaze turned away as he spoke, like he couldn't meet her eyes. "I'm sorry," He said again, his voice suddenly softer. "I've only had to do this once before, and it almost… it almost ended very badly. But I don't have any other choice."

"Doctor, you're scaring me," Clara said slowly, backing up. "What… what's going on?"

"I'm so sorry." He turned towards her just for a moment, his eyes glistening with tears, and then turned away, toggling a few levers. Something dropped down from the ceiling, a sort of helmet with lots of cables and wires. Clara stood, dumbfounded, as he pulled it closer to him and settled it on his head. The ground lurched, but he gritted his teeth and held it against his skull.

"What are you doing?" Clara jumped away from the Doctor as a piece of metal fell from somewhere high above, scattering sparks between them.

The Time Lord's hands were shaking. "I'm disguising myself!" He called out over the sounds of the TARDIS sirens that had erupted into noise again. "These are clever aliens—Oh, they are good. Their technology rivals that of Time Lords, but we have one distinct advantage over them: they're blind! They've smelled me, but that sense isn't particularly sharp, either. They've smelled me and they can sense me and the TARDIS, which is how they're pursuing us. They can tell that I'm a Time Lord and that I've got a very important piece of technology with me, but that's it! If I change that, they won't be able to detect us at all, and they'll hopefully give up within the month!"

"Well yeah," Clara shouted over the sirens. "But how do you do that? You can't just stop being a Gallifreyan!"

"That's where you're wrong!" The Doctor was typing furiously at a keyboard on the edge of the control board. He raised one hand to tap at the helmet. "Chameleon arch: Very complicated technology, quite rare and very painful. But it works. It rewrites my biology, changes every single cell in my body from Time Lord to human. They won't be able to smell me. We lie low on Earth for a while, live out normal lives and leave the TARDIS shut down so she can power up again, and then when they leave, we go back to normal! Okay?"

Clara's voice rose in panic. "I'm sensing another 'but' here, Doctor!" She yelled as the sirens wailed louder, their red lights washing the whole room in an eerie color.

"Well, yes, I suppose there is one," The Doctor called back at her. "Unfortunately, the chameleon arch is a little too effective—it wipes my memories, too, and leaves me with a whole other life in my head. I won't remember any of this, which means that it becomes your job to make sure I don't… do anything stupid, like cut my hair or get rid of the bow tie. You know, normal things!"

"Where do the rest of your memories go?" Clara asked.

Frantically, the Time Lord dug something out of his pocket and tossed it at her. Clara realized it was a small, golden pocket watch, etched with symbols in Circular Gallifreyan. "My entire being, this part of me, will be contained inside that watch!" He said. "When we're safe, you can open it and I'll be back to normal. But you absolutely cannot open it otherwise, unless it's an emergency or you're sure we're safe!"

Clara panicked, and almost tossed the watch back at him. "But what if I lose it or something? You keep it!"

"No, Clara." The Doctor, still wearing the helmet and trailing cables, stepped over a piece of broken metal and closed her hand carefully around the little timepiece. "I trust you to keep that part of me safe. Now, back up, I don't want to accidentally hit you."

Clara stumbled backwards as the Doctor slammed down a lever on the console. The last thing she heard him say was, "Get us out of here after this!" before his entire body convulsed and he collapsed to the ground, gripping his head, screaming in pain, his eyes screwed shut. Clara ran to his side, ignoring the sirens and looking desperately for a way to help him, but he didn't seem to respond to her shaking his shoulders. Gradually, the sounds of the TARDIS faltered and slowed. The lights dimmed, flickering shakily from red to orange, and still the Doctor stayed curled on the ground, screaming, shaking. She wasn't sure how long they sat like that, but finally he convulsed one more time and fell silent. Clara realized he was unconscious.

While she had been focused on him, the sounds of the TARDIS had faded away. The lights were almost all off, except for the glowing Police Box sign above the doors. Clara remembered what the Doctor had said about needing to get them out of there, so she gently unlatched the chameleon arch from the Doctor's head and grabbed him under the arms. The TARDIS was filled with chunks of smoking wreckage that must have fallen from the ceiling, but at least the explosions had stopped. Clara guessed that the ship had shut down, probably to power back up after the Doctor used all of the reserves on the shields. It took a lot of maneuvering, and the unconscious Time Lord was quite a bit heavier than she'd expected, but Clara finally managed to pull him out of the doors and onto the street. She carefully slipped her arms out from underneath him and straightened up, wincing as her back cracked in protest.

It was nighttime, and they were somewhere—Clara wasn't entirely sure where yet, but it looked like the edge of a city, where urban met suburban and there were lots of little shops but no big skyscrapers. The TARDIS had parked itself in a little gap between two shops, in a dark alley littered with trash and rusty bins. It was chilly out, and Clara shivered as she hooked her arms under the Doctor's and dragged him a little further out. She glanced down the street, glad to see that it was mostly deserted. Dragging a man down the sidewalk was sketchy enough, but she imagined it would be even worse at night. Clara set him down again and rubbed her shoulders, groaning softly. She wondered if there was a motel nearby.

"Hey! Are you all right?" Clara heard footsteps and the sound of footsteps coming up behind her. She turned to see a young woman with curly hair and olive skin, a loose brown coat around her shoulders and the most uncomfortable-looking pumps Clara had ever seen on her feet. Her bag was slinging loosely at her side, and she looked more than slightly alarmed.

"Oh! Yeah," Clara said. "I'm fine. Just, um… He isn't."

"What happened to him?" The woman crouched down next to the Doctor's unconscious form and nudged him with one hand.

"Too much to drink at the pub," Clara told her, the lie coming a little too easily. "I was hoping to find somewhere close by to put him for the night. Is there a bed and breakfast around here?"

"No, sorry." The woman looked up at Clara. "But is he your friend? You could take him back to your house for the night, couldn't you?"

Clara suddenly realized that she and the Doctor didn't even have a place to stay. "Oh." Her mind scrambled for another lie to cover for them. "I don't have a place right now, actually. Or… Or anything." There was no way she'd even consider dragging the Maitlands into this. "And he was my friend." She smiled softly down at him. "I'm not sure he will be when he wakes up."

"Well…" The stranger trailed off and straightened up. "It just so happens I'm looking for a flatmate. Do you want to stay with me? And I guess we can bring your drunk friend back, too, for the night."

"Oh, I don't know. I don't really have a lot of money, and I'm kind of out of a job…"

"The rent's paid for the next two months, so you can get back on your feet before you need to help pay. And I live right down the street." She pointed behind her.

Clara opened her mouth for a second and took a breath. "Yeah, okay. That'll work. Um…" She stuck out a hand. "I'm Clara."

"Nina." The woman shook her hand and smiled. "Now come on, I'll help with your friend."

"Thanks." Clara leaned down to hook her arms under the Doctor's again, and Nina picked up his legs. They made a rather odd spectacle, two young women carrying an unconscious man down the street late at night, but fortunately no one was around to see it.

Nina's flat turned out to be just a few houses past the little shops the TARDIS had landed between. She unlocked the door with one hand and pushed it in with her hip. "My old flatmate just moved out, so all the furniture's still here," She explained as they carried the Doctor inside.

They set him down on the couch in the little living room, and Clara let out a long breath of relief. "Thanks again," She said. "I was starting to get kinda worried I'd have no place to stay."

Nina smiled. "No problem! Your room is first door on the left down the hall." She yawned. "I'm going to take a shower and then go to bed. You're welcome to do whatever." She ran a hand through her curly hair and yawned again. "G'night."

"Night," Clara replied as her new flatmate wandered off down the hall. When Nina had gone, she sighed and sat down on the couch, next to the sleeping Doctor. "I really, really hope we're still friends when you wake up," She whispered, squeezing his hand tightly. Out of curiousity, she pressed two fingers to the inside of his wrist, wondering if he really had only one heart now. She'd felt the four-beat melody of a Time Lord's pulse before, when she had grabbed his wrist to pull him along with her.

Her fingertips felt the faint, two-pulse beat, and she removed them with a sigh. He really was human now. She stood up and looked back at him one more time, then forced herself to turn away. Her hand slipped into her pocket and she ran her fingers over the etches of the watch. When she opened the door to her room, she was too tired to do anything but flip the light out, flop down on the bed and fall asleep, her hand still clenched tightly around the little timepiece, the part of the Doctor's soul he had placed under her care.