Sam coped with it on a cavern-bycavern basis. If there was a sky-sea below her eyeline, then that direction was 'down'. If the sky-sea was above her then it became more sky than sea and that direction was 'up'. If the sky-sea was opposite her, in the far wall of the cavern, then she just had to walk around for a bit until she could fit it into some kind of perspective.

At length she found herself clambering over a lip of the ubiquitous black rock, a pink sky-sea flowing and churning far behind her. She'd been attracted to this lip of rock because above it was a narrow crack, through which poured what appeared to be daylight. Earth daylight.

She climbed through the crack into a cavern which took her breath away.

A slope of white sand ran down towards a beach which seemed to stretch on for ever. Ma.s.sive pillars of rock rose like stacks of dominoes from the white sand. Through the middle of the cavern ran a cylindrical sky-sea, golden bright like the sun. It hurt to look at it, and its further ends were lost to distance.

The whole place was bathed in its golden glow and Sam's heart surged in her breast. It was one of the most beautiful sights she had ever seen.

She climbed over the ridge and ran down the slope, her feet scuffing white clouds into the golden air.

It was a slope only in appearance, of course. In this low gravity she felt almost weightless, and, as she'd discovered, up and down were entirely subjective. Looking back, she saw that she had climbed through a crack in the side of a cliff of grey rock. It looked as though something had made the hole. Something intelligent.

If she squinted, she could just about convince herself that she was on a Cornish beach, in blazing sunshine. She walked across the sand, and, as she pa.s.sed one of the columns of black rock, she became aware of a sound. She thought she was hallucinating at first, but she could definitely hear it. The sound of children laughing, splashing water. Playing.

She crept round the side of the column, and saw two small figures beside a pool of liquid which sparkled and dazzled, reflecting the sky-sea. She gasped. For an instant, she'd taken them for human children, but now she could see that they were alien. For a start, their skin was pale green, the colour of apples. They were small, about three feet high. Their limbs were thin and sticklike, and they had webbed feet. They were clothed in pale-blue leaflike garments, and their heads were elongated, with small red mouths from which flicked black tongues, and the occasional excited hoot. Their heads were covered in a ma.s.s of feathery yellow 'hair' from beneath which peered perfectly round blue eyes. The overall impression was of a frog crossed with a fairy-tale pixie.

They were capering, their movements perfectly at ease in the low gravity, tossing pebbles across the pool and shrieking with unmistakable laughter as a black appendage flailed about, trying to catch the pebbles, scattering bright splashes of liquid which rose and fell languidly. It was a scene of such normal childish merriment that Sam felt irresistibly drawn to the small creatures.

But something held her back. She knew that appearances could be deceptive. Perhaps this was one of those crazy places where the ugly things were good and the cute things were evil. But what choice did she have? She could go on walking for hours, or even days, and not come across any other signs of life. She'd eventually die of fatigue or thirst. Was that stuff water? She licked her dry lips and her stomach rumbled. Would she be able to eat the same things as these creatures? An image of the Doctor preparing one of his recipes in the TARDIS kitchens flickered into her mind.

She crouched down, keeping close to the pillar of black rock, intending to creep up slowly on the alien children. The shoulder of her T shirt caught on a spur of the spongelike rock. She reached up to dislodge it and some of the rock crumbled away, falling soundlessly to the white sand.

She held her breath, watching the children. They had seen her, and now they were staring straight at her. One of them was holding a pebble, which it threw into the pond. It fell with a plop. The black appendage slipped below the surface.

No point in concealing herself now. Time for first contact. She emerged from hiding, putting on her best smile. 'h.e.l.lo,' she said. 'I'm Sam Jones. Don't suppose you know any decent sandwich bars?'

Their reaction was instantaneous. They ran up to her, dancing around her, their voices high and squeaky. Sam felt their tiny hands on her jeans, tugging at her Mansun T shirt.

Sam couldn't help but laugh. She stooped down, and one of them leapt on her back. It weighed next to nothing. The other capered before her, babbling. Then the one on her back gave a squeak, leapt down and scuttled off with its companion.

Sam followed them. They had run around the far side of another of the pillars. She didn't want to lose them they were the first sign of intelligent life.

Then two figures stepped from behind the pillar of rock, and Sam stopped in her tracks.

They were as tall as Sam, and similar to the 'children', the same green skin and blue eyes. Their hair was paler, almost white, and they wore a darker, more intricate type of clothing with ropelike leggings. The one on the left was dressed predominantly in red, the other in a mixture of purples and blacks. They stood, barring her way, arms hanging loosely by their sides.

'h.e.l.lo,' said Sam, getting ready to run. 'Do you know when high tide is?'

The creatures exchanged glances, and then lunged in unison, grabbing her, their movements surprisingly swift. They pushed her across the sand towards a thing which looked like a giant lilypad. The children peeped over the edge, staring at Sam.

She clambered on to the thing, and was shoved to the back, where a leaflike seat awaited her. She sank into its soft embrace, and tendrils emerged, whipping around her body, holding her tightly in place. She struggled briefly, but that only made them grip tighter, so she stopped.

The 'adults' were busying themselves at the front of the vehicle, adjusting stemlike controls. She felt a movement from beneath and they began to rise into the air.

'Who are you? Where is this place?'

But they weren't listening to her, as they took off over the beach and headed up into the golden sky.

The children were staring at her with round goggle eyes.

Perhaps it was the children. Perhaps they thought she was going to hurt them. 'Look, let me go, I wasn't going to harm your children.'

The one in red turned to her. His voice was fluting, almost musical, and he waved his hands in smooth, flowing gestures.

But she couldn't understand a word he was saying. Of course. Separated from the TARDIS, she wouldn't have the luxury of universal translation.

That might be a problem.

The creature stopped hooting, and turned back to the controls of the flyer.

Sam peered over the edge. They were borne aloft by the motion of flippers arranged around the edge of this giant 'lilypad'. Crazy. Would only work in this low gravity, she supposed. They were flying high in the cavern now, far above the 'beach'. Here and there, glittering pools shone brightly against the white sand. It was getting brighter all around, and Sam realised with a jolt of shock that they were heading straight towards the sky-sea.

Chapter Nine.

Beneath the Twilight Forest Professor Jennifer Nagle walked briskly along the dull concrete-floored corridor, allowing herself a big grin of satisfaction. It had been the first time she'd smiled for days. She just couldn't believe her luck. The Doctor, here, right at the time of crisis. It was just like all those stories the UNIT guys told. Mysterious things would start happening aliens emerging from sewers or people being transformed into the slaves of some despotic computer and then the Doctor would appear, in one of his many guises, solving the problem in a display of dazzling brilliance.

That was what she needed right now. The Doctor's brilliance.

She'd been studying theoretical physics at Princeton University back in the 1970s, when Earth had seemed to come under attack from an alien or home-grown menace every other week. And yet this was kept secret from the entire world. After she got her PhD she did a little digging around and soon discovered the existence of UNIT. A United Nations setup dedicated to combating alien menaces, hiding behind a skilfully constructed mask of disinformation. There was a huge cover-up going on, and she desperately wanted in. She craved the thrill of walking among the common people and knowing knowing. Of being elite.

One day, in her rented apartment, she'd had a visitor. A well-dressed English man in his fifties, who told her all she wanted to know about UNIT and offered her the ultimatum of either joining or waving goodbye to her career for ever.

She remembered even now the way her scientific zeal ('curiosity' was way too lame a word) had blossomed. She had said yes right away. She just wanted to know. Know everything. She wanted to discover new worlds and new processes and be rewarded for doing so.

That was twenty years ago. Joining UNIT had been the best thing she had ever done. She'd been based in the US at first, rising to Professor of Theoretical Physics at Princeton. After that, her attachment to UNIT had taken her all over the world. And now, thanks to her hard work and one incredibly lucky discovery, she was deeper in, involved in research kept secret even from most of UNIT.

Professor Nagle quickened her pace. She had to get to the Doctor before Major Wolstencroft did, before he was 'interrogated'. She reached a door, outside which a UNIT soldier stood, rifle held across his broad chest, barring the way. He had a youthful face, close-cropped hair and pale-blue eyes. English, like most of Wolstencroft's men, and fiercely loyal.

She resented the presence of so many troops, but, after the events of the last few days, it looked like they'd need them.

'Private Schofield, isn't it?'

The soldier nodded, eyes fixed on a spot on the wall opposite.

She sighed. 'Well, aren't you going to let me in?'

'Pa.s.s, please.'

She waved a hand irritably. 'You know who I am, so let me in.'

'Yes, ma'am.' There was the trace of a smile on his face.

A pointless show, a reminder that Wolstencroft had stepped up security several hundred notches.

Private Schofield stood aside and Nagle entered the observation room. It was a small, boxlike s.p.a.ce with three swivel chairs behind a monitoring unit. A two-way mirror spanned the far wall.

Two men looked up as she entered. The one on the left was Captain Daniel Rogers, Wolstencroft's right-hand man an OK guy despite that. And next to him, Dr Boris Lindgard, the Swedish expert on extraterrestrial life. Lindgard was one of the few people in the base apart from the soldiers who had actually been outside. Nagle hadn't ventured outside for almost two years now. Lindgard was good almost too good; a cold, calm professional. He'd been able to infiltrate the hospital with ease with a little help from HQ, of course. He'd brought in the creatures from the forest, the body of Johan Svensson, and now this. The Doctor. The G.o.d from the box, who would save her reputation.

Through the two-way mirror Nagle could see the debriefing/detention room. Sitting on the sofa was a man with wavy golden-brown hair and an intelligent, long, sensitive face. He was wearing an expression of studied boredom, with just a hint of tension in the set of his shoulders and around his eyes.

She'd not seen this incarnation before. He was by far the best-looking, and the best-dressed: dark-green velvet frock coat, patterned waistcoat and a white wing-collar shirt with a cravat neatly tucked into the waistcoat. A smooth, unruffled, timeless look. Much better than hold on now. How could she be sure this handsome stranger was the Doctor? 'Are you sure that's him?' she said, slipping into the chair next to Lindgard.

'Oh, yes,' said Lindgard. 'That is certainly the Doctor.' He spoke English well, along with a dozen other languages, some of them alien. A key factor in his selection for the job of man on the outside.

'This one's been turning up ever since 1997,' added Captain Rogers. He had close-cropped red hair and a thoughtful, freckled face. He laughed, showing perfect white teeth. 'That's the trouble with the good old Doc always a few versions of him knocking about.'

Lindgard shot him a withering look. 'The captain is quite correct. The man in there is the eighth incarnation of the Doctor. I myself have also encountered the seventh.' He looked at the Doctor, a smile playing over his thin lips. 'Believe me, this one is far easier to deal with. Far more predictable.'

This was good news. 'As long as you're sure.'

'Believe me, it is him,' said Lindgard, a trace of impatience creeping into his voice. He smiled coldly. 'And now that I've got him for you, what do you want to do with him?'

Captain Rogers coughed. 'Well, the major will want to interview him. As a matter of security.'

Lindgard blew out through his lips. 'I don't think we have time for that.'

'We certainly don't,' said Nagle with feeling. 'I think it's time Major Wolstencroft realised who's in charge.' She leaned past Lindgard and addressed Captain Rogers. 'You guys are just here to protect us and keep outside eyes from prying, got that? Leave all the important stuff to us.'

Captain Rogers blushed visibly, but his eyes were defiant. 'We'll see,' he said tightly, and left the observation room.

Lindgard raised his eyebrows. 'One day you'll provoke them too far.'

Nagle shrugged. 'Yeah, but what can they do? We're their paymasters, after all.'

She reached out and pressed a switch on the desk in front of her.

The Doctor sat on the sofa, a cushion in his lap. He stroked it absently, as if it were a cat.

'Sorry for booting you like that,' he mumbled. 'Had to let it out somehow and you see you're a mere inanimate object. Though I've met many life forms which look like inanimate objects.' He was talking to himself to keep the panic down, until either something happened or he thought of a means of escape. 'The Ogri, for a start. Look like monoliths. Or is it megaliths?'

Suddenly a voice came from a hidden speaker, and the Doctor jumped to his feet, the cushion falling forgotten to the floor. It was a calm, professional-sounding, female voice, with an American accent the Doctor placed in Seattle or probably New York. 'Do not panic. You are safe. I am Professor Jennifer Nagle, Chief Scientist of this installation.'

Good, thought the Doctor at least I'm speaking to someone in charge. 'Then you can doubtless tell me why you have brought me here against my will?'

There was a pause. Then: 'We have brought you here because we believe you can help us.'

They were very close to the sky-sea now. It was blinding, like staring into the sun, and Sam had to sit, eyes tight shut, so that her world turned red and black. She could hear the two creatures hooting instructions to each other.

'You're not gonna fly into that thing, are you?' she yelled, knowing they couldn't understand her, but unable to keep the panic down any longer. The pink sky-sea had been safe enough but this one looked hot, as hot as the sun. She opened her mouth to scream, struggling against her bonds, convinced that she was about to be burnt to a crisp.

But it didn't happen.

Everything got brighter and brighter and then went back to normal.

Sam opened her eyes.

They were inside the sky-sea, travelling along it. It was like being inside a golden tunnel, stretching ahead into the distance. The stuff of the sky-sea wasn't wet, it exerted no pressure, and she could breathe normally. 'This is too weird,' she breathed, relieved nonetheless.

The creatures ignored her, standing impa.s.sively at the prow of their leaf-vehicle, while the children oohed and aahed.

The Doctor would love this, thought Sam. It seemed to be three things: a sky that wasn't a sky, a sea that wasn't wet and which gave light and a sun that you could travel inside, without getting burnt instantly to nothing.

At length, they emerged from the tunnel of light into a wider area of sky-sea. They broke the surface to emerge into a vast cylindrical cavern, whose walls expanded and flowered into a trumpet shape. As they rose up, Sam could see hundreds of brown domelike dwellings dotted about on the walls, and just make out dots of green, where the froglike creatures moved.

There was something above them, some sort of structure. As they grew nearer Sam realised how big it was easily as big as a city. It hung from the ceiling of the cavern, an onion-shaped ball with spiralling towers and minarets, all formed from a dark-green material, shining with lights.

The leaflike flyer drew closer and closer to one particular tower, towards an opening. They flew inside, into a wide long hall, filled with a milling crowd of the creatures.

Ah. The crowd were above them, seemingly standing on the ceiling, and they were flying up to them Sam's mind boggled, and she made a quick adjustment.

And she now saw that the crowd were standing on the floor of the amphitheatre. The air was thick with their cries. They all seemed to be in a great rush about something, and this mood pa.s.sed to the pilots of the leaf-vehicle, whose hootings had become to sound rather stressed. The children cowered in a corner, their round blue eyes shining in the golden light which streamed in from the sky-sea miles below erm, above, or whatever.

Their flyer settled down and Red and Purple disembarked. The two young creatures ran off into the crowd, soon to be lost out of sight amid the bustle. Sam was alarmed to see that the adults did not seem to notice or care about this.

A crowd had gathered around Sam. She felt as if she were at a slave auction. Perhaps that was what this was all about. Green faces and blue eyes peered at her from all directions. Sam shook off their probing hands. 'Hey, get off.' After a while they began to lose interest and drift away.

Her original captors led Sam across the arena to the other side, shoving through the crowd. The sense of panic was palpable, and contagious. Sam felt light-headed with hunger and exhaustion.

Red pulled her towards what looked like a giant finned aubergine, which she presumed was another sort of low-gravity dirigible. Other hands grabbed her, shoving her inside, into a leaf-seat next to some spindly creatures which resembled giant praying mantises. Tendrils emerged from under the seat, binding her firmly. She sighed, settling back, resigned for the moment. Despite the restraints, it was actually quite comfy.

She looked at the creature next to her. It was a pale-bluish colour, its six legs covered in thin silver bristles which kept tickling Sam now and then. Its head was flat, ovoid, with black compound eyes at the edge, and mandibles hidden underneath near the jointed neck. It chittered at her and rubbed its forelegs together, making a noise which set Sam's teeth on edge.

One of the froglike creatures was walking up and down a central aisle, handing out chunks of a brown fungus-like stuff. The Mantises ate it hungrily, and Sam saw some of the frog-things tuck in, too. Sam took a piece, wondering briefly if it would be poison, but she was tired and hungry, so she ate. It tasted remarkably good, like a floury fruit with a hint of cinnamon.

Soon they were airborne, above the crowd. She looked out of the slitlike window to her left. Below, the creatures were silent, staring up at the dirigible. It was an eerie sight a sea of alien faces, lifted up towards her, their yellow white hair contrasting with their green faces and varying pastel shades of their costumes.

The dirigible sailed out of a wide opening in the side of the amphitheatre. Above or below the sky-sea glowed at the bottom or top of the cylindrical cavern, looking for all the world like a sun. The dirigible plunged down and down, back towards it, and Sam had to shield her eyes from its glare.

She chewed her last mouthful of food, trying to put together what was going on. Where was she? Who were these creatures and what were they afraid of? And, most importantly, what were they going to do with her?

Fitz and Kerstin had followed the three men to a small clearing, and they now hid at the edge in the cover of the trees. Moonlight threw everything into sharp relief the wooden cabin in the centre of the clearing, the white-suited figures approaching it, opening the door and stepping inside.

Kerstin shifted restlessly. 'This just gets weirder,' she said. 'What would they want in there?'

Fitz glanced at her. Her face still held a strained look, especially round the eyes. 'Depends what's in there. What is it, something to do with the farm?'