'It wants a physical existence again, don't you see?'

'And it's got it, largely thanks to you as I recall.'

'Not quite,' the Doctor said. 'Not yet.' yet.'

'I heard it trying to break the lab door down earlier. I'd say that was pretty physical.'

'Yes, but only there; only on the other side of the door.

Out here, it's still formless, existing only as shadow.' The Doctor sat forward, energised by his own train of thought.

'Why?'

'It's getting darker,' Cadwell said. 'I can hardly see a thing. Switch your torch on again.'

'It is is on. The Doctor held the pen torch up. Its tip glowed faintly. 'But it's fading... Wait! That's it! Cadwell, I think you've got it!' on. The Doctor held the pen torch up. Its tip glowed faintly. 'But it's fading... Wait! That's it! Cadwell, I think you've got it!'

'I have?'

'The Dark can only achieve physical existence in complete complete darkness. darkness.

That's why it was able to hurl itself against the lab door - it was completely completely dark on the other side. But out here it's still light.' dark on the other side. But out here it's still light.'

'But not for much longer.'

The Doctor glared at the failing pen light. 'Worrying, isn't it?'

Tegan eased herself down through the jagged gap, found a narrow foothold with the tip of her shoe, and then fell the rest of the way. She landed in a heap in the sand.

Her torch rolled a few feet away, the business end buried in the dust.

For a long moment Tegan was in total darkness, spitting out the alien grit and exercising her swear words.

It was so so dark. dark.

She had a flash of memory, right back to her early childhood: not wanting to go upstairs to the bathroom on her own. Not straying out of her bedroom in the middle of the night unless her Dad came for her, answering her call.

She had an urge to call out for him again, now.

Her fingers closed on the torch and pulled it from its its grave. The light shone weakly, picking out bits of metal she couldn't identify. 'Nyssa? Are you there?' grave. The light shone weakly, picking out bits of metal she couldn't identify. 'Nyssa? Are you there?'

No answer. She swept the light around but there was nothing here but bits of s.p.a.cecraft wreckage. They stuck out of the sand like old tombstones, throwing up big shadows.

But no Nyssa.

She thought of checking the sand for footprints, but it was useless.

Everything was mixed up and swirled around; the tracks could have meant anything.

But there was no doubt about it: Nyssa was gone.

The shadows were moving. They were deepest in the far corners of the cave, and up in the dim recesses of the cavern's roof, but the Doctor could see the shadows thickening there. The blackness was somehow more intense, almost intrusive, as if it was too black for this universe.

The darkness gathered itself, crept closer, stronger, colder.

Cadwell sat hunched against the rock, sweating with fear. His face was drawn. 'That torch won't last much longer.'

The Doctor gave the pen torch a shake. It was pointless.

The light was feeble. 'Where are they with that flare?' he muttered.

'Dead, probably. We could be the last ones left alive, and now it's coming for us.'

The Doctor had to aim the torch right at Cadwell to see him now. His bald head glistened in the shadow. He was taking something from the pockets of his uniform jacket; several metallic components that he began to fit together with a series of sharp clicks. 'What's that?' asked the Doctor, pointing the torch at Cadwell's shaking fingers. The light glinted off a small handgun. 'What're you doing?'

'Like I said, I'm not waiting around for the Dark to finish me. I'll do it myself, first'

'Don't be stupid.'

'Stupid? It's the only intelligent thing left to do, Doctor. If I'm going to die, it'll be on my terms.' Cadwell slotted a magazine into the b.u.t.t of the gun. He looked up at the Doctor. 'You might want to die screaming like an infant. I do not.'

The Doctor grabbed hold of his wrist. 'I can't let you do that.'

'You can't stop me. If necessary I'll shoot you first and then do myself. Clear?' Cadwell stared at the Doctor. They were very close and Cadwell only had to whisper. 'Believe me, I'll be doing you a favour.'

'Be quiet.'

Cadwell raised the pistol and pressed it against his own head.

'Goodbye, Doctor. It's been -'

'I said be quiet.' quiet.'

Intrigued despite himself, Cadwell hesitated. 'What?'

'Look,' the Doctor instructed. 'And listen.'

The darkness had clotted in the centre of the cave: there was no ignoring it, no denying it. A ma.s.s of blackness, too much blackness, bulging out of the shadows like a tumour on reality. It hurt the eyes to look at it, as if all the available light was being painfully sucked into nothing.

They could hear it, too. A faint rushing noise at first, like the hiss of a distant waterfall, but growing louder all the time.

Soon it sounded like the roar of a crowd, a thousand voices raised in exultation - or torment.

A million voices, crying out for mercy: screaming in agony and despair.

'The people of Akoshemon,' said Cadwell, his voice barely a breath in the Doctor's ears. 'Or the things they became...'

The Doctor gritted his teeth, unable to block out the searing river of anguish as it poured down the centuries.

'We're too late. It's here' With a rising howl, like a million souls tortured beyond the point of madness, the Dark solidified. Shadows rushed towards it like children to their mother. It grew darker, and deeper, with every pa.s.sing second and each additional shadow.

Something huge cast it's shade into the universe.

The pen torch's tiny bulb died. The Doctor and Cadwell were embraced by the darkness.

It heaved and sucked and clawed its way from nowhere, right in front of them. They couldn't see it. But they could hear its first guttural breath, feel the rancid air on their fear-p.r.i.c.ked skin. The blackness pressed against their eyes, filled their ears, probed every orifice with a clammy urgency.

Something moved in the dark, heavy and wet as a bath full of worms. A cold, moist finger touched the Doctor's face.

Up until that point the Doctor had kept his eyes resolutely, pointlessly open. Now, as he felt its first touch, he shut them tight. The finger moved slowly over his nose and lips; the gentle caress of a drowned lover. The Doctor began to shake.

I've come for you, Time Lord...

The light, when it came, was sudden and brilliant and intense. The Doctor's first thought was: I'm dead!

Then he realised he was glad he had shut his eyes.

Lucky he had shut his eyes, because even through the lids he could see the light: a hazy, painful red that made him flinch so hard he struck his head against the rock behind him. he had shut his eyes, because even through the lids he could see the light: a hazy, painful red that made him flinch so hard he struck his head against the rock behind him.

He clamped his hands over his face and twisted away.

The light was scalding, blinding, penetrating.

He could hear something: a whoosh of air that was like a scream of agony or a shout for help, he couldn't tell which.

He realised the light had faded when the scarlet fog was gradually replaced by a fuzzy darkness.

He opened his eyes. They were watering, but he could see. The cave, empty of darkness, lit by the dying light of a minuscule sun at its centre.

There was someone lying there, face down, a woman with dirty blonde hair tied in a ponytail. She was clutching something in one hand.

The Doctor crawled quickly over. 'Stoker?'

She lifted her head and looked at him. Her eyes were darting.

'Doctor? That you?'

'Relax' His voice was thick with relief. 'You're all right? 'I can't see!' Stoker said, panicking. 'I'm blind!'

'It's all right. It's temporary. The zenesium flare has stunned your optic nerves, but they'll recover.'

She fumbled her way into his arms.

The Doctor said, 'You saved my life.'

She let out a sob. 'I didn't save Lawrence.'

'It wasn't in your power to save him.'

Stoker's eyes were clearing, beginning to focus. She winced. 'h.e.l.l, but you look awful.'

The Doctor pulled gently free. There was a sore spot on his cheek and he fingered it tentatively. 'I think the Dark touched me. Just before you arrived with the zenesium flare.'

'I didn't know if it would work,' Stoker said after a while, nodding at the forgotten flare. 'When I got here I couldn't see anything, it was so dark... dark like I've never seen before.'

'You arrived just in time.'

'Is it dead? The Dark, I mean?'

'I don't know.' The Doctor stood up stiffly and turned to Cadwell.

'What do you think, Cadwell?'

Cadwell was still sitting propped up against the rock wall, staring at nothing.

'Cadwell?' The Doctor knelt down next to him. Cadwell didn't move.

His eyes were blank, his lips slightly parted. He looked shockingly pale, almost completely white: the veins beneath his skin stood out like roads on a map.

Stoker rubbed her eyes. 'What's happened to him?'

'The Dark must have got him,' said the Doctor quietly. He gently shut Cadwell's eyes, but the pupils were still visible through the eyelids.

'He's almost transparent,' said Stoker.