It was Christmas time, and everybody's features had somehow started blending- the blond hair, the sick grin, the sound of the drums. A minor setback for humanity, but Rassilon soon fixed that, a snap of the fingers. Everything back to normal.

What the Doctor didn't realize that day, the day he died, was that Rassilon's cure didn't work immediately on every human on the planet. It varied from person to person. A man in India was shaking with the transformation for hours after his family. A teacher in New York spent the entire rest of the night trying to get the drumming out of her head. For a nurse in Leadworth, it took twice as much time as it did his fiancée to change back into human.

And the Master, as he lay dying, felt himself out there out the world. A living, breathing Time Lord on Earth. And he flew to the nearest version of himself, zipped himself into this man's consciousness even as humanity reigned its control over the man's body. The Master fell back into the shadows again. Alive.

It might have stayed that way, too. He might have died when his host died at the end of a natural human lifespan, and that might have been the complete and final end of the Master from Gallifrey. And maybe in a parallel universe, that's how it went.

But this is not that universe. This is the universe where Rory Williams ran away with the Doctor, and was reminded. This is the universe where the Master woke up.

"Rory!" He felt Amy's arms on his shoulders first, shaking him, and then he felt the cool glass beneath him. The TARDIS floor. The lights. "Rory."

"I'm… fine." He sat up, the back of his head searing. He must've smacked it against the floor. Amy was kneeling beside him, worried, and the curved walls around them were spinning a bit. The whole scene had a somewhat hazy hue, like the afterimage of a very bright light. "What happened?"

"Sorry!" called the Doctor. He seemed to be jumping in circles around the center console, throwing switches and pulling levers. "Hit a spot of turbulence, temporal energy from the engines started sort of… leaking." He glanced at Rory apologetically, but there was something else in his expression, something Rory couldn't quite pinpoint. "Knocked you over."

"Are you alright?" He swiveled his gaze back to his wife and noticed that she, too, had something in her eyes other than sheer worry about him having a concussion.

"I think so," he said, grabbing one of the railings to pull himself into a standing position. "Head hurts…" She rose with him, eyes wary. "What is it? Why are you looking at me like that?"

"Are you sure you're okay?" she said, running her hand over the back of his head like she was checking for a lump.

"I'm fine," he said. "I fell down, is all."

"You were laughing."

"What?"

Amy squinted at him carefully. Out of the corner of his eye, Rory could see the Doctor still working over the console, looking as though he was trying very hard to not say something. "After you fell," explained Amy. "You were lying on the floor and just… laughing."

"Um," said Rory. He blinked. "I don't… remember."

"No telling what pure time energy will do to humans," said the Doctor, swinging around to face them. He gave a well-meaning smile that didn't reach his eyes. "You should probably sit back down, Rory."

"Yeah," he agreed, moving to one of the folding chairs they'd set up. "My head's pounding." He sank down, massaging his temples, and he felt his son-in-law's eyes on him. That same expression, vaguely familiar and not at all reassuring.

"How about a little fresh air?" said the Doctor, grinning at Amy. He jerked a switch and the TARDIS grinded to a halt. As the engines whirred and settled, he slid into his jacket, straightened his bowtie, and took Amy's hand. "Come along, Ponds."

As Rory straightened up to follow them out the door, it suddenly hit him why the Doctor's expression had been familiar. He'd seen it before, back before Melody was born, in the way he'd looked at Amy- well, Amy's Flesh duplicate. When she hadn't been who she was supposed to be.

"Ah," exclaimed the Doctor, stepping into the smoggy London morning. He checked his watch. "Nineteenth century."

"This is your idea of fresh air?" coughed Amy as Rory came to stand beside her, still clutching his head. "Industrial Revolution?"

"Anything beats New New York at rush hour," he said, sweeping the couple away into the bleary day.

They walked for a bit, but after too many close-calls from getting waste thrown at them from upper windows, the Doctor decided to buy a loaf of bread and find a bench in the park. They sat, the Doctor sandwiched between his in-laws, and munched on bread. After awhile, Amy started tossing some to the ducks swimming in the pond in front of them.

"They look sick," she said of the waterfowl. Rory tapped absently on the wooden bench. "It's this air."

"Well, that's the human race for you," said Rory, chewing on a piece of bread. "Destroy the world for every other race living there, but hey, if you can make a little money." He swallowed without noticing the strange look the Doctor was giving him. He did, however, catch the affronted glance from his wife. "What?"

"Nothing."

When they had finished the loaf of bread, the Doctor stood, stretched, balled up the plastic wrapping from which the bread had come and tossed it to Rory. "Go find a bin for that, will you?" As Rory headed off to the other side of the park, Amy felt the Doctor reach for her hand. "Don't look back," he said into her hair as he pulled her away from the bench and away from Rory. "Don't stop. Just walk."

Without really pausing to think, Amy did as he said, advancing out of the park and onto the street. He kept a firm hold on her hand. "Doctor, what's-" she started, but then Rory must have turned around and noticed them leaving, because suddenly the Doctor's hand was tighter on hers and he was full-out running, pulling her with him.

She ran. Of course she ran, it was what they did. She'd been doing it since that blue box first appeared in her backyard. And so they reached the TARDIS before Rory could. The Doctor slammed the door shut and sonicked it, hearing the lock click into place.

"Doctor, what is going on?" said Amy, leaning against the side of the TARDIS. "Why did we leave Rory back there?"

"Listen, I told you about the Master," he started.

"Bad Time Lord, yeah?" said Amy. "What's he got to do with it?"

"So much," said the Doctor. He looked scared, genuinely scared in a way that Amy hadn't seen him in a long time. "More than I thought. Did you hear Rory tapping on the bench?"

"No," she said, sounding appalled and confused. "What? What's wrong with Rory?"

"Rory isn't Rory," said the Doctor, rubbing his brow. He could hear footsteps outside, now. Rory had realized what they'd done and was running for them. "You have to trust me. I don't know how, but he's… him. He's the Master."

"Doctor, you're being ridiculous," she said, reaching for the lock.

"Listen to me," the Doctor pled, grabbing for her wrist. "Just listen how many times he knocks. Four times. It'll be four times." Amy stared up at him, baffled and unconvinced. "He will knock four times."

"I'm letting him in-" Knockknockknockknock. She froze.

"Doctor!" Rory called from outside the door. Knockknockknockknock. "Doctor, what is it? Did you see something?" Knockknockknockknock. "Let me in."

The Doctor didn't make a move. He just watched Amy. Watched to see what she would do. She too, did nothing. Just stared at the door. She didn't touch the lock.

Knockknockknockknock. "Amy?"

"Why are you doing that?"

Knockknockknockknock. "Doing what?"

"Knocking, Rory," she said, almost breathless. "Just stop knocking." He did.

"What's going on?" he said through the door. "What happened? Was it the ducks? Were those alien ducks?"

"Rory," said the Doctor carefully, painstakingly choosing his words. "Rory. Listen. Knock three times."

Perplexed as he was, Rory complied, hoping if he did this would all make sense sooner. Knock. Knock. Knock. The Doctor exhaled and moved for the lock. Knock. With his eyes closed, the Doctor stiffened. "Rory?"

"I can't…" Knock knock knock. Knock. Knockknockknock. Knock. "Why can't I do it? Why… there's drumming…" There was a rustle against the door, like he'd slid to the ground, and then a soft thudding. He was thumping his head against the TARDIS in frustration, still in a rhythm of four. The Doctor looked over at Amy, who was breathing in and out too quickly.

"Doctor," she whispered. "What-"

"Keep this door shut," he said in an undertone, pointing to the lock. "Don't come out. Don't open it." And then he stepped out, leaving her alone in the TARDIS.

Rory was slumped on the ground, looking and feeling like hell, beating his head against the police box to the beat of the drums that had flourished in his head and stayed there. He wasn't really paying attention, but suddenly the Doctor was stooping in front of him.

"What's happening to me?" Rory's eyes were frantic and searching. He felt like he was dying, or going insane, or possibly both. He was sure he'd gone insane before- two thousand years, waiting for Amy, with nothing to keep him occupied but his poison false memories. Of course he'd gone insane before, but he'd always got back to somewhere stable. He'd always come back around. This time felt different.

"I need to talk to you," said the Doctor.

"Then talk."

"No," he said, eyes dark. He was too calm, too quiet. Here was the Oncoming Storm in his element. "Not you, Rory." He put his hands on his friend's temples. "I need to talk to the man who's being hiding inside your head."

Rory's head snapped forward, mind reeling, hyperventilating, and when he looked up he wasn't there anymore. He let out a low laugh, soft and sinister. "Did I surprise you this time, Doctor?" It was Rory's face, Rory's voice, and yet it was so far from him. That tone, the look in his eyes- so horrible and familiar.

"I suppose I've had this coming," said the Doctor. Rory- the Master- smirked. "How did you do it?"

"It just sort of happened," he shrugged. "The universe must love me." He yawned and stretched out his arms like he was testing them. He ran his hands over his face. "Nose."

"Why now though?" said the Doctor, silently hoping that Amy couldn't hear their conversation. He couldn't keep the anger out of his voice. The betrayal. Because even though the Master had saved him and the Earth the last time they'd met, albeit out of a need for personal revenge, he was still the Master, a creature of torment and hatred and destruction. He didn't want Amy to ever associate this Gallifreyan with her husband.

"Time energy knocked me back into focus," he said. "Before that, I was just an easily forgotten nightmare. A shadow on his consciousness." His expression faltered, and he braced himself against the TARDIS as if he felt he might spill off the surface of the Earth. "I was the drums. And it was all I was. And it was all I had, for years."

"I'm sorry."

"Oh, you're always sorry," said the Master. "The Doctor in the TARDIS, always sorry, always so, so sorry." He was watching him cruelly, but there was something else too. "What if I forgive you?" The Doctor remembered pointing a gun at his head. He remembered watching him send the Time Lords back into the war.

"You're a better man than I thought you were," he admitted. And for a moment he could see it- he could see himself giving the Master a second chance. That was who he was, wasn't he? A creature of forgiveness, of second chances. But… "But you're still not as good as Rory Pond. Give him back."

"Um…" he said, pretending to think about it. "No."

"You're a Time Lord consciousness living inside a human," said the Doctor. "You'll burn his mind if you stay in there any longer."

"I don't need his mind; I've got my own," said the Master.

"Leave him."

"I'll die," he said. "Is that really what you want? My blood on your hands?" There was turmoil in the Doctor's eyes. "It is, isn't it? You want me dead. You want to be done dealing with me. You want me to go away-"

"Me," the Doctor said suddenly. "I'm a Time Lord, I can hold you. Leave Rory and live in me." With his hands still on Rory's head, he could feel the brain inside heating up. He could feel what remained of Rory dwindling as the Master smirked with Rory's face, and the Doctor realized with a worried start that he really didn't know what was going to happen, and then there was a flash of yellow light.

And then the Master was in his head. It was like nothing the Doctor had ever experienced before- two lives, two consciousnesses, battling it out in his mind. He tried to stay focused. Keep Rory and Amy safe. There was no telling what the Master would do if he got control of the Doctor. He could trick the Ponds. It would be so easy, just to tell them-

Keep Rory and Amy safe. The Doctor staggered upward, put a hand on the TARDIS door. He could hear the drumming. Tu-tu-tu-tum. Tu-tu-tu-tum. Keep Rory and Amy safe. Tu-tu-tu-tum. Two mantras, two minds, collapsing inside him together.

"Doctor?" Rory's voice sounded shaky, but reliably him. "Doctor, what happened? My head…" Keep Rory and Amy safe.

"Get in… the TAR…" He pulled out the sonic screwdriver and unlocked the door before staggering in, muscles twitching. Two wills pulling at him. Rory. Amy. Safe. Behind him, Rory stumbled in the door and looked to Amy. The Doctor reached the console and flung open his toolbox. Rory. Amy. Tu-tu-tu-tum. He rifled through various items- egg beaters, staplers, a lighter- and pulled out a watch. Tu-tu-tu-tum. Amy. Tu-tu-tu-tum.

"You're you, aren't you?" Amy said awhile later, thumping Rory on the shoulder as if to ascertain that he was really, solidly there. "You're really, properly you?"

"Feels like it," he said, and he kissed her. "I'm back to normal, aren't I, Doctor?"

"Oh, Ponds," said the Doctor, watching them fondly from across the TARDIS. "You know there's no such thing as normal." Amy smiled at him and the Doctor reached into his jacket pocket. The thumping from the watch came softly but surely, and too insistently to be the ticking of an ordinary fob watch.