Up above, a branch creaked. Somewhere in the distance, a thanator thundered past, but it was soon gone. It was quiet.

Suddenly, an alien, thumping, grinding noise rang through the forest, and with it, an even more alien object faded into existence. It was big, blue and at least a century out of date. There was a camp of aliens nearby, and they would have understood the object instantly, if only because they could read its sign: POLICE PUBLIC CALL BOX.

The door opened. "Ah, Pand—glur—" the Doctor choked, diving back inside and closing the door behind him. Nothing happened for a few minutes. Then, the Doctor appeared again, saying, "...Apart from the atmosphere, it's brilliant. Just don't annoy the—"

"Doctor, what do you mean apart from the atmosphere? What am I breathing?" said Rory, following close behind.

The Doctor kneeled down to look at something. "Just sulfur hydroxide and... oh, yes, carbon monoxide. Don't worry about it, it gets eaten by the jiggery-pokery."

Rory spluttered, pulled himself together and turned to Amy. "Am I the only one who's worried about that?"

She hesitated for a moment before saying, "Yes. We're alive, aren't we?"

"Well, yes, but carbon monoxide is toxic."

"Rory, you managed to survive for 20 centuries made of plastic, a little bit of poison won't hurt you," joked the Doctor, still watching his plant intently. Amy walked over and knelt down beside him.

"...It's glowing," she realized, and started laughing. "Ferns don't glow," she said in disbelief.

The Doctor poked at it, and Amy jumped as it zipped into the ground. He just smiled.

Meanwhile, Rory was looking at a nearby tree — glowing dimly, like everything else. There was an arrow embedded in it, quite easily as long as Rory himself and thicker than his arm. "Doctor..." he started.

"Yes? Oh. Ooooh..." said the Doctor, as he noticed the arrow.

"What sort of people live here?"

"That's odd," answered the Doctor in his usual disconnected fashion. "They don't miss and even if they did miss all the blood here's green and this thing's old..." he said as he waved the sonic screwdriver over it.

"Doctor," Rory interrupted.

"...Sorry, yes, they're—"

A thunderous crash shook the earth, and all three of them fell over.

"—not industrialized," he finished, getting up. He waved the screwdriver in the air. "...That's radio noise, thermal noise, even Q-wave traffic, someone's got a nice reactor..." He stopped, and consulted the as-bare-as-always screwdriver. "Nobody here should have a Clarke-Bester generator," he said, and ran off into the glowing forest.

Amy and Rory glanced at each other. Amy shrugged, and they ran to keep up.

There was an awful lot of running with the Doctor.

They caught up with him as he stood on the edge of the forest, looking over the crest of a hill. "Oh," he said, as he came to a stop. Amy slid up behind him. Although she didn't say anything, she had the same surprised look on her face.

" They're not...?" Rory began.

" They're not. This isn't them. This can't be them, they'd be really annoyed if this was them, that certainly isn't them," the Doctor said, looking up slightly.

What they saw, near the foot of the hill, was a military base. It was huge, busy and blocky. Jeeps drove along tarmac roads among angular, metallic buildings, and lines of gray smoke trickled out of several chimney stacks. The Doctor watched an aircraft of some sort, the same gunmetal gray as the rest of the base, lower itself vertically towards a landing pad near the perimeter. He adjusted his bowtie, and turned to his two companions.

"If I told you you shouldn't try to wander nonchalantly into a military base, because it's really, really dangerous," asked Rory, half-hardheartedly, "would you listen?"

"No, sorry," the Doctor said, turning around and heading down the hill.

The three of them ended up on one side of a hangar at exactly the moment the aircraft they had seen earlier landed on the other. The back door of it swung open, and the Doctor urgently ushered the three of them around a corner when he saw what it was carrying: a squad of troops. They waited, peering around the corner, while the troops marched out and past them. "Doctor, what's going on?" Amy asked.

"I don't know," he said, stepping out. He ducked back as he realized another group was coming, but simply stared as he saw what it was. It was a single man, wearing a gas mask and using an archaic, manual wheelchair. He rolled past without acknowledging them.

"Surely they've got rid of wheelchairs in the future?" Rory piped in.

"You get the neurosurgery to fix spines in 2051 and you don't get lightdrive until 2088, well, that's when it's officially released, though the prototypes came out as early as '85, but the malfunctions were a bit messy and-"

"Doctor, they're looking at us," interrupted Amy, watching a pair of suspicious guards some distance away.

"So they are. I wonder why that is. It's 'cause we're not wearing gas masks, isn't it?" he said, turning to Amy. The guards started walking towards them. "Oh, well, when in Rome, do as the Romans do."

"And when you can't do what the Romans do?" asked Rory.

"Run!" the Doctor said, doing exactly that.

They ran through the maze of buildings, taking three left turns, a shortcut sideways over a set of pipes, and then diving under an overpass before taking a final right turn to end up, out of breath, in front of a small door.

"We've lost them," said the Doctor, casually.

"Look, can we not do that again?" Rory panted. "Or at least, can we have some clue what's going on?"

"Right, yes, sorry, this is Pandora," the Doctor said. "It's one of the most beautiful places this side of Orion's arm, but last time I was here, humans weren't, and since this place is completely useless tactically, something else is going on, and I'd like to know what. Shall we invite ourselves in?" he said as he waved the screwdriver at the door. There was a click, and it swung open slightly.

Through the door, they found themselves in a small, grimy airlock, next to a small rack of respirators. The Doctor waved the sonic screwdriver against the inner door, before standing back, puzzled. "Why's that door so complicated?" he muttered.

"We're not stuck, are we?" asked Amy.

"No, but new plan," he said, reaching across to the rack. "Put a mask on and I'll ring the doorbell."

After a moment, the Doctor pressed a promising-looking switch by the door, and they all jumped at the sound of an actual doorbell. The trio shared incredulous looks while a voice said, "Mitchell's getting annoyed about this. He says just to lock you out next time, OK?"

"OK! Won't happen again!" replied the Doctor confidently. The door opened, and they ended up in yet another gray metal corridor, though the feeling of claustrophobia was lessened somewhat by the unusually high ceiling.

They walked along the tunnel for a few meters, before coming across two doors, almost opposite each other. The Doctor opened one as Amy listened at the other. She heard a deeper voice say, "I dissected a frog once," while the Doctor concluded, "Broom closet."

"Barging in might not be the best idea," suggested Rory meekly.

"It's worked so far," the Doctor said, barging through the door.

The door opened into a large circular room, lit by bright blue light coming from a central ring of a console, surrounded by a larger ring of devices that looked suspiciously like tanning beds. In the centre of the ring stood an older, tall woman, who snapped at the Doctor, "Who are you?"

The Doctor confidently flashed the psychic paper.

"The next coming of Vishnu? Haven't you lot taken enough piss already?," she said. The Doctor twisted his hand around to look at the paper himself.

"Oooh, it's never done that before," he said, but stopped as he realised the woman had turned to a younger man behind her.

"Why would the next incarnation of Vishnu have I.D. to that effect?" the man asked quizzically.

The woman turned back to the Doctor, "I'll try again: who are you?"

"I'm the Doctor, this is Amy and that's Rory," he said, gesturing around himself. "I don't think we're affiliated with Vishnu, but then again, I can't be sure."

"This isn't some deranged joke from Quaritch, is it?" the woman said, turning sideways to a man beside her in a wheelchair.

"They weren't on the shuttle, I'd have noticed," he replied.

"But then... how...?" she mused, before realizing something else. "We're wasting time. You," she told the man in the wheelchair, "get in."

"I'm sorry, I don't believe I caught your name?" the Doctor asked innocently.

The woman sighed and waited a few seconds, trying to calm herself down. "I'm Dr. Grace Augustine, this is Norm Spellman," she said, gesturing to the younger man behind her.

"And Anachronism Man?"

"Jake Sully," she said, indicating the man in the wheelchair, who was pulling himself into a tanning bed.

"I recognise that name," the Doctor said suddenly. This got stares not only from Jake himself, but also from Rory and Amy. "Except I can't remember why," he continued, with sudden confusion, "What year is this?"

"What year is this?" Grace said, incredulously.

"2154," Norm provided.

"Right," said the Doctor, walking around the room to the nearest bed, waving the screwdriver as he went, "only last time I found something that odd I ended up having to reboot the universe from scratch, although, I suppose a chair's lighter than a mech which would be important here, but that doesn't really explain your lack of sp— no, the USMC should p—"

Suddenly, the Doctor froze. He slowly turned to focus on Jake, and said, "You didn't actually say the words, "It's too expensive for VA," did you?"

"No," he said.

"And nobody's actually told me you've been in the Marines, did they?"

"No."

Slowly, a smile crept across the Doctor's face, before he squatted down and read a nameplate attached to the bed. He stood up and turned back to Grace, before saying cheerily, "What are you doing with type 40 FBX neuron transceivers that needs 12 of them active at once?"

Grace framed the word, "You—" before she gave up and said, "It's for the avatars," gesturing to a window occupying one side of the room. On the other side was a white room, sterile and organised. In the room, in the manner of all mad scientists everywhere, were several gurneys, each supporting an unconscious, blue humanoid. "You know what an avatar is, don't you?"

"Doctor, are those gangers?" said Amy from beside the window.

"What are gangers?" said Grace and Norm simultaneously.

"OK, not gangers," she said.

"Gangers are robot duplicates from about forty years from now, though obviously the ones you've got aren't the same species, but—" Another ominous pause. "...Nevermind, can't fix that right now. Why do you need them?"

"The goons upstairs pissed off the natives, and now they shoot any human they find. We were trying to negotiate out of killing each other," Grace replied.

The Doctor was looking out of the window, through to the clean-room. "You on good terms?" he asked, flatly.

Grace sighed. "Not really, no. That's what happens when you slaughter the natives for the rock they're living on."

"Why does that sound familiar?" Rory suggested sarcastically.

"Gold was never worth $20 million a kilo, but yeah, we've not got rid of greed yet. Maybe in another 300 years."

There was a pause.

"I'd like to talk to them," the Doctor said suddenly.

"Can't be done," responded Grace curtly. "An avatar is grown to a specific genome, and they take five years to grow."

"Only because you're doing it in inefficiently. Everyone stay here, I'll be back in a sec," said the Doctor, vaulting over the ring in the centre of the room and heading for the door he came in. When he passed through the door, he stopped opposite the broom closet, and announced "One!" He then counted his way along the corridor, and quickly faded from hearing.

There was a few seconds of silence, before Norm said, "Is he always that mad?"

"You...er, get used to it," Rory replied.

Grace had walked over to Jake, who had been sitting in one of the steel tanning beds. With it open, both Rory and Amy could see that describing it as a "tanning bed" would be like describing a Swiss watch as "a few gears." As she closed it, something in the distance went clank, and the console in the centre of the room beeped a few times.

As she walked over to another tanning bed, Grace froze in mid-stride.

"...Forty years from now...," she re-wound. "How, exactly...?"

"We're time-travellers," said Amy.

"And I was just about to believe he actually was Vishnu's next avatar," Grace sighed, "Norm, could you plug in and make sure Jake doesn't hurt himself?"

Norm started walking across the room, on a path that took him across the central console. One step, two, three, thump, as he walked into a police box that had not been there a split-second before.

"What," said everyone.

The door creaked open, and the Doctor's young, enthusiastic face leaned out. He said, "I used the boring-ers!" before stepping out into the room proper.

"You're blue!" said Amy.

"You've still got the bowtie..." said Norm.

"Bowties are cool," cut in Amy, before clapping her hand over her mouth when she realised what she had said.

"You've got a tail," said Rory. There was a muffled clang behind the window. The airlock at the far side of the room was shut, and one of the gurneys was conspicuously empty.

"You... just..." Grace spluttered, waving a pointing finger between the Doctor and the TARDIS.

"In order: tails are cool, I think Jake agrees with me, and I'm sorry for not explaining before," The Doctor said, smiling, "I'm a mad man with a box."