Rory dropped a bit of pocket lint on the path behind them. He was running out of clues, which was unfortunate, because he didn't have a clue about what to do next, except wait for the things with teeth or the Cull or what-have-you to come and get them.

He was having problems managing this relationship.

When Rory was studying nursing, one of the first things he learned was never to contradict a doctor in the performance of his duties. Most of the time, this did not present a challenge. Almost all the doctors Rory had known were competent enough, and truly odious ones were... routed around. At the hospital, there was a whole system for minimising mistakes, or, if that was impossible, making them disappear. A really good nurse could keep an entire wing ticking over like a Swiss watch, without upsetting any physician's sense of authority. It was just fancy footwork.

Rory used similar tactics on the Doctor. Rory never put his foot down on any issue. Instead, things that needed to happen just sort of happened. Like leaving the second moon of Krensk. They'd had no adventures that time. No hanging about, no falling in dark holes. It was just: land, take one peek out the door, and hey-what-happened-to-Krensk. When Rory didn't feel like fighting—which was always—he could be incredibly difficult to pin down.

None of this would be news to the real Doctor. The two of them had a deep understanding. As long as that understanding held, everything was All Right, and since any other state of affairs would be hurtful to Amy, the understanding would always hold. It was absolutely rock-solid. This had all been quietly sorted about fifteen seconds after Rory had first set foot on the TARDIS.

You could be jolly mates with almost anyone, under such circumstances.

Rory's current problem was that the boat had been upset. "The teacher" might someday be the Doctor, but all of the hard work Rory had put into managing him was yet to pay off. All of the safe topics—Amy, the TARDIS, warnings and instructions—were off limits, since they concerned some complicated and specific revelations about the future. Furthermore, all the risky topics—the past, the future, and philosophies and approaches about same—were suddenly in play, if Rory was supposed to make this ill, alarming old man into the Doctor.

Added to the soup were Rory's, for lack of a better word, medical instincts. A man in such a state as this old teacher was to be treated gently. Rory's vision for this man's immediate future included a bowl of thin soup and an early lights-out. He had a lot of trouble reconciling that with his view of the real Doctor, whose immediate future usually included lizards, crash-landings, River Song, or some combination of the above.

For all that, the teacher moved like something was right on their heels. He barely leaned on his cane, but used it to tag the walls. In some places it was almost like looking into a skylight. In others, the man's harsh blows would only kindle a ribbon of light. No matter what, he never left them in complete darkness. As they moved, anger seemed to radiate off him, growing with each step and giving him strength beyond his fragile health. He was damn fast with that stick, Rory observed, and Rory had to step carefully to avoid being smacked.

The long and short of it: there was silence.

Rory tried to fill it by cajoling his one college psychology class out of the recesses of his memory. He had not gone in for Mental Health. Hadn't seen a future in it. But a bit had stuck out, and that had been the bit about post-traumatic stress disorder. Not that he had ever suffered it personally—though he was currently evaluating it as an option—but it had helped him understand Amy. Even before Time had gone weird on him, Rory had known about people who got stuck on the past. For example, meeting the Doctor as a little child, then getting promptly abandoned by him. That sort of thing was difficult to get over all at once. You had to process it. It kept coming back at you in different ways.

Rory chewed his lip. It didn't quite fit. Yeah, sure, the Doctor was a little bit cracked, but he hadn't been any worse lately. They hadn't done anything traum—ahem, unusually traumatic. A bit of a hangover from the business at Stormcage, maybe, but that was mostly physical; even Rory had some bumps and bruises from that. It was no worse than anything else. So why had they come here?

"Ha," muttered the teacher. The stick whipped out and slammed into the wall, conjuring red light. "That's what I want to know."

The stick was in front of Rory like a barrier. "What?"

"What's that?" said the teacher, his own private thoughts interrupted. "Oh, don't mind me. Carry on." He gave Rory a dark stare and inclined his head in a strange sort of bow. He pulled the stick away and kept walking, forcing Rory to jog to keep up.

"Where are we going?" said Rory, because he had to say something.

"Some place with a hell of a lot of noise."

"Noise?"

"Oh yes," said the teacher. "Some rushing, sort of thing, lots of crashing, maybe some screaming. Like the Fortress of Solitude." He pointed ahead of them. "It's just up there."

"The Fortress of Solitude didn't have screaming."

"Oh, well, there you are," said the teacher.

In fact there was a soft rushing noise coming up on them, which Rory recognised as the icefalls. Apparently they went all the way through the cave system. He felt a light draft and wished he'd worn a heavier coat. The sound reminded him of the picnic they'd had just a few hours ago. It seemed like a different, faraway time, and Rory supposed it was. Technically, it was still in the future. If he waited long enough, would he catch up with himself?

"I sincerely doubt it," said the teacher.

Rory came up short again. He felt a bit dizzy. He put a hand on the cool wall. "I didn't say anything out loud."

"No," said the Doctor, but in such a way that Rory couldn't tell if it was a statement or a question.

Nevertheless, all the hairs went up on Rory's neck. "You can hear what I'm thinking?"

"There it is," said the teacher. Sensing that Rory wasn't going to be getting much further for a moment, he turned and leaned heavily against the wall. He caught his breath. "That was sort of like a scream."

Rory was stunned. He was, for a moment, silent on every level.

"Don't look at me like it's my fault," said the old man. "You're the one putting all the effort in. I don't care either way."

Rory glowered. He still hadn't got his mind around it.

"Look," said the teacher, a bit impatiently. "When I said noise, I meant it. The falls are very loud and in a place like this, they echo. You couldn't speak in here if you wanted to and anyway, the Fa'dkin Chvet can't talk. So you tell me, 'Rory': when was the last time you actually spoke? Because by my count it was more than an hour ago. Keep walking." The teacher pushed himself off the wall and stalked away.

"But I can hear just fine," said Rory. It was normal conversation, wasn't it? He tried to think of it in a different way and couldn't. It was just talking. He was badly frightened, but he followed. He didn't want to be left alone with himself. "I'm fine."

"Yes," said the teacher. "Like I said before: it's very interesting."

They stepped into a chamber. Rory felt the room open up around them. Then the teacher's arm shot out and the stick hit the wall.

It was lightning. If this was a mine, they'd hit the motherlode. White light filled the room, traveling from the old man's cane outward and upward, until the whole room filled was filled with a brilliant glow. On the far side of the chamber the icefall crashed. The fall Rory had seen up above was tiny compared to this.

"Hundred decibels in here," said the teacher, in a perfectly normal tone of voice. "Like a damn jet engine. But here we are."

Between the young man, the teacher and the falls were a huge gathering of Fa'dkin. More poured in from various hallways, or drifted from high above. There was no way for Rory to recognise his "friend" from before—to him, they all looked more or less the same. But he could hear their silent fear and anger, their sense of violation, and he knew that he was in serious trouble.

The end was nigh, and so on.

"You have about thirty seconds to explain yourself," said the teacher. His voice was calm and pleasant. Confident, was the word. This was the voice of a man who had the drop on a deadly enemy. And Rory, to his profound and lasting terror, couldn't even remember if the teacher was speaking out loud. "Who are you? What are you? Why did the future Doctor bring you here? Because I'll tell you something: it hasn't been that long since the war. Not for us. And we don't tolerate your kind around here."

"M-my kind. But I'm... I'm just..." Rory backed up until he hit a wall.

Shadowman, he'll find us. Shadowman, I warned you.

Well, yes, Rory thought desperately. But it didn't mean it that way. I'm mean, I'm not the...

"Yeah, he did mean it that way," said the teacher. "There is a shadow following you. I can see it. And if you think you can come here just because I'm dying—if you think you can outsmart me—then you are in for a bad surprise."

"Please," said Rory. He held up a hand. "Listen to me."

High above their heads, even louder than the falls, there was a horrible knocking sound. Something at the door.

Before Rory could say another word, the ceiling fell in.