'No, it isn't.' The Doctor finally finished shaking his head, as if he'd only just noticed he was still doing it. 'The point is, somewhere around here is an object which only exists at specific predetermined times. I convinced the TARDIS to materialise in phase with it, so whatever the object is, we should be able to find it whenever we like. In theory, anyway.'

Sam clicked her fingers. 'I get it. So, when you said we were being watched...'

'I was talking about Somerset's leopard.'

'Come again?'

'Somerset's leopard. Genetically enhanced panther. Developed on Earth during the 2050s, used as guard dogs by the very rich. Quite a status symbol in j.a.pan, I believe.'

Sam realised his eyes were fixed on something behind her. She duly turned.

She didn't see anything much, but then, in an environment as full of stuff stuff as this one, there was plenty you could miss. Lots of colour, lots of detail. Saplings with brilliant green leaves, overripe fruits that looked like exhausted mangos, sparkling yellow blooms sheltering between the trees... as this one, there was plenty you could miss. Lots of colour, lots of detail. Saplings with brilliant green leaves, overripe fruits that looked like exhausted mangos, sparkling yellow blooms sheltering between the trees...

Yellow blooms. Perfectly circular yellow blooms, each with a black slit running from top to bottom. Yellow blooms that only grew in pairs, and only in those heavily shaded areas where the forest canopy stopped the sunlight reaching ground level.

The yellow things moved. Staying in pairs. Several wide, cat-like faces began to emerge from the shade, the "blooms" twinkling in their sockets. The background noise of the rainforest, the twitterings and scratchings of the insects, was backed up by a ba.s.sline of low growling.

'Not the kind of wildlife you'd expect to find here,' the Doctor went on, helpfully. 'In fact, the ReVit ecosystem isn't designed to accommodate any large predator, although usually '

'Doctor,' said Sam.

'Hmm?'

'What exactly are we going to do?'

The Doctor cleared his throat. 'Very good question. Remind me, did I ever tell you about "Plan B"?'

Lieutenant Bregman looked up at the ziggurat, and tried to remember how to be impressed. Being impressed was harder than it sounded, right now. Partly because she was exhausted after the trek through the forest, but mostly because having seen an alien Lost City appear out of nowhere in the middle of a mapped ReVit Zone it was going to take more than smart architecture to make her go funny at the knees.

And wasn't that the first sign of Displacer Syndrome? Accepting the bizarre, the alien, the downright stupid, without question? After the first couple of Cyberman incursions, most of the poor sods who'd managed to get out of UNISYC had ended up either founding religious cults in LA or developing what the military psychiatrists called "extended Quixotism". Seeing windmills as giant alien attack robots, believing tiny little men were living inside their TV sets, that kind of thing.

All of which made Bregman think of her superior officer. Kortez was standing at her side, staring up at the stone frontage of the ziggurat. Every centimetre was covered in tiny little ideograms. Bregman wondered if the Colonel was trying to read them all.

'Sir?' she said. He didn't respond. 'Sir, there's n.o.body here. We were supposed to be met. The invitation...'

'There's somebody up there.'

'Sir?'

'On the roof. There's someone standing on the roof.'

Bregman looked up, but she couldn't see anyone. All she saw were the huge stepped layers of the building, towering over the rest of the City. All of a sudden, she felt incredibly nauseous.

When she looked down again, Colonel Kortez had vanished.

'Lieutenant?'

Bregman jumped. There was a tunnel in front of her, a rectangular opening in the front of the ziggurat. Another one of those appearing-out-of-thin-air-without-any-warning things, Bregman told herself, and she surprised herself by not being very surprised. She could see the Colonel standing in the pa.s.sageway, flanked by torches, the firelight bouncing off the hard edges of his face. He was looking back at her impatiently, not understanding why she hadn't followed him in yet.

So Bregman followed him in.

The tunnel was strangely comfortable. No carpets or furnishings, but comfortable anyway. The walls were smooth, unmarked by the s.p.a.ceman carvings, and somehow the light from the torches managed to make the place look cosy instead of horrifying. The corridor felt like it had been air-conditioned, although there weren't any visible signs of ventilation. The chic of an Incan ruin, thought Bregman, but with all the mod cons thrown in.

The pa.s.sageway widened out in front of them, eventually becoming a four-way junction. The Colonel stopped moving. The man had a vaguely bemused look on his face, Bregman noticed. But then, he usually did. When things weren't what they seemed.

'You're correct, Lieutenant,' Kortez told her.

'Sir?'

'We should have been met. Recon.'

'Recon? Colonel, I don't '

'You will stay here, at the point we will refer to as junction number one. You will wait for my return, or for the arrival of the party we're due to meet. Is that clear?'

'Yeah, but... I mean, is that our best option, Sir? If we're separated...'

'This is not to be considered a hostile environment, Lieutenant. This is a mission of diplomacy. We are not to antic.i.p.ate aggression of any kind.'

Bregman coughed apologetically. 'Yes, Sir.'

Kortez nodded, then marched off along the pa.s.sageway directly ahead. Bregman watched the way he moved. Stiff limbs, mechanical movements. He walked like he talked, she thought. She tried squinting into the darkness in front of him, but she couldn't see the end of the pa.s.sage, not from here.

'Terrific,' she hissed, as soon as he was out of sight. She wrapped her arms around herself. Not that she was cold. You couldn't be cold, out here in the Indies. She felt exposed, though, had done ever since she'd arrived on the island. Being here, in the alien stronghold, didn't make her feel any more secure.

Alien. Oh, Jesus, yes. Kortez had seen someone on the roof, he'd said, but he hadn't gone into detail. At the very least, Bregman should have asked. Somebody human? Somebody humanoid?

She remembered the book, the little pocketbook, the one she'd been issued with when she'd been awarded 19-L security clearance by UNISYC Central. Typical of UNISYC, it had been called The Eye-Spy Book of Alien Monsters The Eye-Spy Book of Alien Monsters, and between the covers there'd been profiles of every ET species the organisation had ever shot at. The Cybermen had been on the first page, unsurprisingly, but the book had gone on to describe such obscure and exciting species as the Martians, the Selachians, the Krynoids, the Hurgalnooks, the Banders.n.a.t.c.hers, and the Rock-Eating Yellow-Bellies.

She'd been ordered to memorise the book, then eat it. Only later, when she'd gained 20-L clearance, had she been informed that the book was a credulity test. Only a handful of the BEMs in it were real. The rest had been invented by some idiot in Central's Training Division. The first sign of insanity, her superiors had chuckled, was when you read the book and believed every word of it.

Oh, and you weren't really supposed to eat it, either.

Somebody spoke.

Bregman panicked.

'h.e.l.lo?' she said. She turned, checked the corridor, saw nothing.

Somebody spoke again.

Too quietly to make out the words, though. Come to think of it, there might not have been any words. Or even any noises.

No noises. Bregman tried to get a grip on what she was thinking. She'd definitely heard something, but it was as if the sound had gone right into her skull, not stopping at her ears first. Subsonics, then? She tried to identify the direction the non-sound had come from, and decided on a side-pa.s.sage, the one to the left.

Uh-huh. But this was a real horror flick moment, right? Cue innocent female character, hearing a noise and going off to investigate alone. Ready to have her arms bitten off by the alien monster round the corner.

Alien monster. Sobering thought, around here. Bregman stopped moving.

The side-pa.s.sage was much like the main corridor, but there were doorways on either side, half a dozen in all. She couldn't make out the far end of the corridor, although that was where the sound seemed to be coming from. Ahead. Ahead, and down.

She listened. No, she didn't need to listen. And it wasn't subsonics, it went deeper than that. If the sound was reaching her brain without touching her ears... telepathy? Maybe. Bregman had been given a "what to do in case of psionic attack" lesson at the college in Geneva, but the advice had been vague; even Central still wasn't sure about the psychic stuff. She tried to remember which of the aliens in the Eye-Spy book were supposed to have telepathic abilities. The Time Lords did. The Quirkafleegs did. Or were they made up?

Bregman suddenly found she was moving again, wandering towards the source of the noise. She stopped.

She stopped right next to one of the doorways.

There was movement from the room inside. Bregman turned her head.

As far as she could make out, the room was almost entirely bare. But then, the furnishings weren't the first thing on her mind. There was a simple bunk on the other side of the chamber, opposite the doorway, a single figure perched on its edge. The figure's feet were on the floor, its shoulders hunched, its features lit by the guttering torches.

It was human. Humanoid. Male. Wearing clothes. What kind of clothes? Bregman found it hard to care. It had a head, a normal-shaped head, and the face...

The face moved as she watched. The skin broke open before her eyes. Folds unfolded, wrinkles readjusted themselves. Sharp white objects, hard and solid, emerged from the flesh.

Smiling. That was all it was doing. Smiling. Oh, G.o.d. The face was just a face, a normal face, but everything that made a human being really human had been sucked out of it. It was as if her mind couldn't accept this collection of features as a face at all. She could only see it as a lump of skin and bone, couldn't attach any humanity to it, the way you were supposed to when you came face-to-face with another living thing.

The man on the bed kept smiling. A dead man's grin. Like he knew what the rest of the world would think of him, and didn't much care. Bregman felt muscles twitch behind her cheeks. She realised some part of her unconscious had responded to him, was trying to smile back. At the same time, her hand was reaching for her belt, trying to find her gun.

But of course, she wasn't carrying a gun. This was a mission of diplomacy. This wasn't to be considered a hostile environment.

'Biodata,' said the Doctor.

'What a-huh a-huh about it?' said Sam. about it?' said Sam.

'I knew there was something wrong as soon as we stepped out huh-huh huh-huh of the TARDIS. We Time Lords have certain of the TARDIS. We Time Lords have certain huh huh mechanisms built into our own biodata. It makes us mechanisms built into our own biodata. It makes us huh-hun huh-hun very sensitive to distortions in the biodata around us.' very sensitive to distortions in the biodata around us.'

'You mean a-huh a-huh like DNA, right?' like DNA, right?'

'Not just DNA. When I say biodata huh-huh huh-huh I mean something that goes deeper than I mean something that goes deeper than huh-huh-huh huh-huh-huh simple genetics. In every cell of every organism, there's a mine of information waiting to be simple genetics. In every cell of every organism, there's a mine of information waiting to be huh huh accessed. For example, supposing you travel through a accessed. For example, supposing you travel through a huh-huh huh-huh fourdimensional fourdimensional huh huh feedback loop in the TARDIS. Because of the various feedback loop in the TARDIS. Because of the various huh huh energies released by the loop, the experience of the energies released by the loop, the experience of the huh-huh-huh-huh huh-huh-huh-huh journey will be encoded into the very journey will be encoded into the very huh huh essence of your biology. If you know how to read it, you can discover the most remarkable things from essence of your biology. If you know how to read it, you can discover the most remarkable things from huh huh bio biohuhdatahuh.'

'I didn't a-huh a-huh know that.' know that.'

'No. Well. The human race doesn't really have much need for advanced biodata technology. Genetics is the only huh-huh huh-huh thing your species really cares about. Of course, genetic information does form part of your biodata thing your species really cares about. Of course, genetic information does form part of your biodata huh huh matrix, but it's not all there is to it.' matrix, but it's not all there is to it.'

'And you reckon a-huh a-huh a-huh a-huh a-huh a-huh someone's someone's a-huh a-huh fiddled with the biodata of these leopards?' fiddled with the biodata of these leopards?'

'I think someone's "fiddled with" the biodata of huuuuuuh huuuuuuh this whole environment.' this whole environment.'

'A-huh. OK. Doctor?'

'Yes?'

'How long have we been running, now?'

'Why? Not out of huh huh breath, are you?' breath, are you?'

'Who, me? A-huh A-huh. G.o.d, no.'

'Good.'

Without warning, the Doctor let go of Sam's hand. She gurgled in protest, lost her balance, and pitched forward. The Doctor had been dragging her along behind him, as if he'd thought she wouldn't have known how to run on her own. All the time, she'd been able to hear the cats pounding through the undergrowth behind them. In the trees, the toucans had been screeching like car alarms.

Sam pulled her face out of the mulch on the forest floor. For the first time, she realised she was in front of a building.

It reminded her of one of those places you used to see on Arthur C. Clarke's Mysterious World Arthur C. Clarke's Mysterious World, an old temple covered in scratchy little stick figures. The building was no bigger than a large shed, built out of stone the colour of dental plaque. The Doctor stood in front of the entrance, idly inspecting the carvings around the archway.

Sam cast a glance back over her shoulder. She saw the undergrowth being pushed aside, saw heavy muscles tightening under coffee-coloured fur. But the Doctor was still inspecting the carvings, as though he had all the time in the world.

He was like that, sometimes. He was like that at the worst of times.

Sam opened her mouth to shout out a warning, but a moment later, he was gone, vanished into the mouth of the building. Sam dragged herself off the ground and stumbled after him.

'Oh, good grief,' the Doctor said to himself.

There wasn't much room to move inside the building; most of the s.p.a.ce was taken up by the machine. To the naked eye, it was a simple cube, six feet along each side, made from the same material as the building itself. Its surface was covered in panels, all engraved with the same tired old pictograms. All the artistic integrity of wallpaper, the Doctor decided.

He stepped closer to the machine. The bits of him that were human insisted it was nothing more than a block of stone. Fortunately, the bits that weren't knew better. He could feel the effect the device was having on the environment, its little manipulations, its biological gravity. His senses had drawn him to it, pulled him here across the rainforest.

He heard Sam stumble into the building behind him, gasping for breath.

'Doctor ' she began.

'Shhh,' said the Doctor.

He bashed the machine, twice, with his fists. Obligingly, one entire panel, two feet wide and two feet high, fell away from the surface. It felt more like plastic than stone, and it bounced when it hit the ground.

The Doctor peered into the s.p.a.ce inside the block, examining the internal workings. The technology was fairly straightforward. Various electronic components were jammed into the interior, superdense plastic cables connecting morphogenic fission vials to the biosensory byput systems. There were also a number of little flashing lights, but he had no idea what those were.

He squeezed both his hands into the s.p.a.ce. Sam was at his shoulder now, sc.r.a.ping his neck with short, nervous breaths. Outside, the whole forest was growling.

'What ' began Sam.

'It's a security device,' the Doctor explained. 'I thought as much when I saw the leopards.'