'No, I don't mean his service record. I mean his personal records: 'I can't.'

'c.r.a.p.'

Lawrence stiffened. 'I beg your pardon?'

'I said c.r.a.p! You're the captain round here, you can do whatever the h.e.l.l you like.'

'I can't access Cadwell's personal records.'

'I'm not so smashed that I can't tell the difference between "can't" and "won't". Don't tell me you're letting some stupid moral code stand in your way? You're a thoroughbred Consortium b.a.s.t.a.r.d, remember?

Scruples don't come into it'

'I can't access his personal files,' Lawrence repeated patiently. 'It's completely against the Consortium's conduct and discipline rules.'

'I don't believe that for a second. You must have a security override.'

Lawrence hesitated. 'It's only for use in emergencies.'

'Right.' Stoker sat forward with a glint in her eye. 'And who around here is authorised to declare a state of emergency?'

For a long time Nyssa's only source of light was the Doctor's torch: its circle of illumination rippled over the craggy ground before them, scouting for unexpected hollows or crevices, leading them deeper and deeper into the freezing darkness.

Eventually the rock started to smooth out, the floor and walls of the tunnel becoming rounded and glossy, as if they were moving down a thick, gla.s.sy tube. The change was not lost on the Doctor, who quickly pointed out that the general effect was, 'almost organic, like the inside of an artery or vein.'

The image did nothing to comfort Nyssa, but the Doctor was intrigued. He pressed his torch against the curving surface and the beam sank into a dull green glow just beyond the surface. 'The translucence is fascinating, don't you agree? I've never seen anything quite like it.

'I'm very cold, Doctor. Must we stop to admire the scenery?'

'Where's your scientific curiosity, Nyssa? Come on, this way.'

She followed him a little further until he stopped dead.

'What's the matter?'

The Doctor sent his torchlight roving further down the tunnel. 'I'm not sure. Time for a little experiment, I think.' And with that, he switched off the torch.

The darkness should have been absolute, but Nyssa was surprised to find that she could still see.

Further up ahead, there was a distinctly green glow. It seemed to be emanating from the rock itself, and after a few moments Nyssa could discern thick, wavering lines of emerald light buried in the stone. The lines wound their way into the distance, creating a wan luminescence that filled the tunnel.

The Doctor hurried forward, inspecting the rock closely.

'Fascinating! Look!'

Deep within the very rock of the tunnel wall were thick veins of light.

The Doctor shone his torch into the rock and the nearest vein moved, as if it was recoiling inside its own narrow tube.

'What are they?'

'Some sort of life-form, I imagine. Invertebrate, probably moving through the rock itself.'

'How?'

'Very slowly, I should think! Perhaps they use existing holes, with a bioluminescent mucous membrane acting as a lubricant to aid movement. Or the mucous could be corrosive, helping them to progress through solid rock.

'I don't think I like the look of them.'

The Doctor was mildly perturbed. 'Nyssa! They're probably harmless: nothing more than very long worms. They probably move about an inch a year or so, and wouldn't survive outside of the rock itself. You've nothing to fear.'

'That's easy for you to say,' Nyssa murmured.

'Let's push on,' said the Doctor.

There was enough light now from the rock-worms to see quite clearly. Nyssa dutifully followed the Doctor's pale, green-hued shape along the tunnel; there was only one direction they could go in now and he seemed to have dispensed with her services as a guide.

'Doctor?'

'Hmm?'

'What do you fear?'

He stopped and turned to look at her, slightly bent in the narrow pa.s.sage. 'Why do you ask?'

'You never seemed to be scared of anything.'

He smiled. 'Never judge by appearances!'

I'm serious. What does scare you?'

The Doctor thought for a moment. 'Well, let's see: I've never much enjoyed the company of Daleks. Or Cybermen.

I've crossed swords with the Master more times than I care to remember, and the Black Guardian is bound to catch up with me one day... but do I fear fear them? Not really: but I do fear the harm they intend, the misery and destruction they can cause.' them? Not really: but I do fear the harm they intend, the misery and destruction they can cause.'

'And your greatest fear?'

'Ah, that's easy. Being out for a duck.'

Tegan watched Ravus Oldeman carefully: he was sleeping in the Adamantium's medical bay, wired up to some kind of computer monitor. The Doctor had told her what signs to look out for and what to do when she saw them, but she hadn't antic.i.p.ated the old man's delirious rambling.

He lay on the couch, covered with a single silver sheet, half-conscious and muttering incessantly. Tegan strained to hear what he was saying. It sounded like something to do with his time as a research technician in the underground lab: she thought he mentioned Professor Garondel a number of times, and other stuff about Akoshemon. In fact, every time he mentioned the planet, the monitor readings spiked alarmingly.

'What is it?' she asked him tentatively. 'What are you trying to say?' His pale eyes opened a crack to look at her.

'Garondel's a meddlesome little fool,' he hissed. His eyes gleamed, diamond-hard, beneath the fleshy eyelids. 'He knows nothing! Nothing!' Nothing!'

The eyes closed and flickered. Oldeman twisted and turned a few times and Tegan glanced nervously at the life-signs monitor. What was this? Some kind of attack? A fit? A flashback?

'The Akoshemon DNA is perfect! Never seen anything like it!'

'It's all right,' Tegan said soothingly. 'Calm down.'

'It's not all right! That interfering little lab rat Garondel's got it all wrong, I tell you!'

Tegan was puzzled, but she jumped when Oldeman's eyes opened again and he reached out a cold, bony hand to grasp her wrist.

'Hey! Let go!'

'Neurolectrin!' he gasped. 'I need the neurolectrin!'

She shook her head. 'The Doctor says you can't have any more, not yet. You're going to become addicted.'

'Rubbish. Give me the neurolectrin, you silly little woman!' Tegan twisted her arm free. 'Not likely!'

'I'm losing my mind!'

'The Doctor says it'll destroy your mind if you have any more too soon.'

Oldeman collapsed back onto the bed, chest heaving.

The medical computer bleeped and something registered on the monitor.

Oldeman's eyes flickered shut and he relaxed as the tranquilliser took effect.

'Should never... have... taken... him on...' he muttered.

'The Doctor?'

Oldeman shook his head feebly. 'Garondel...'

The pa.s.sageway had narrowed dramatically, and the glow-worms had petered out: the Doctor and Nyssa were left inching their way along in perfect darkness once more. The Doctor brought his torch back into play, just as the tunnel widened out into a vast, low-ceilinged cavern.

At first Nyssa thought they had stumbled into some kind of weird, subterranean forest. The Doctor's torchlight fell on a number of thick, gnarled grey trunks sprouting from the cave floor like trees. They were densely packed, no two more than a metre apart, some as thick as a man and others slender enough for Nyssa to encircle with both hands. The torch beam was trapped and snared among the trunks, which seemed to continue in haphazard array for as far as as they could see. they could see.

'How very odd,' the Doctor remarked. His voice reverberated unnaturally through the eerie forest.

'What are they?'

'Stalagmites,' he replied. And stalact.i.tes. The former growing up from the cave floor to meet the latter as they come down from the roof. Interesting phenomenon.

The conversation echoed through the cave and disappeared in a ghostly moan. Nyssa shivered. 'It's horrible.'

'It's certainly going to make things a bit tricky' the Doctor said. 'Stick close: we don't want to get separated in here.'

Nyssa followed him into the granite forest, one hand resting on his shoulder. They picked their way through the stalagmites, forced to take a winding path that she found utterly disorientating. After a couple of minutes they were completely surrounded by the ghostly grey columns.

The Doctor flashed his light around them and they could see nothing but the stalagmites disappearing in every direction. Nyssa felt as though they were closing in on her.

'Which way now?' she asked, terrified that the Doctor was going to admit he was lost.

'Down, I think.'

'Down?'

'The ground is sloping away, hadn't you noticed?'

She shook her head and followed him. The ground was indeed sloping downwards, and now the gradient was becoming quite marked. They slipped and stumbled through the rock trees, holding onto them for support when necessary. To the touch the stalagmites were as cold and hard as bone but coated with a thin slime. Eventually the forest began to thin: the stalagmites grew slimmer and shorter, some of them failing to meet up with the stalact.i.tes hanging down from above. Soon there were none that came above knee-height, and the Doctor and Nyssa were able to duck beneath those that grew overhead. It felt uncomfortably as though they were clambering out through the serried teeth of a shark's jaws. Beyond lay total darkness. The Doctor pointed his flashlight into the void and they saw the beam reflect from a glistening rock wall cut with an arched tunnel entrance.

'That looks manufactured,' whispered Nyssa.

'It certainly isn't natural,' the Doctor agreed.

The mouth of the tunnel was bearded by silvery cobwebs. Hundreds of spiders clung to the web, but scattered as the Doctor brushed the strands aside. Beyond was a ragged, black hole. He stepped cautiously into the opening and his torchlight found the walls. They were slick and black, and cut with thousands of short, jagged marks in rows.

'h.e.l.lo, what's this?'

'Those marks are deliberate,' Nyssa said, frowning.

'Looks like the writing's on the wall,' the Doctor said.

'These are ancient runes of some kind.'

'I don't like them,' Nyssa said quietly. 'They're a warning.

I know they are.'

The Doctor glanced at her. 'We won't know for sure unless we can read them. They might be some form of greeting.'

'Do you honestly believe that?'