The men looked uncertainly to Cadwell for orders.

Cadwell pursed his lips and said, 'Then what do you suggest, Doctor? An ambush, perhaps? We could all stand here and wait for it to return for dessert.'

'Is sarcasm all you have to offer?'

Cadwell smiled grimly. 'Let me know when you have anything useful to contribute, Doctor. In the meantime I shall begin another search for the creature. You can escort Miss Jovanka to the Adamantium, Adamantium, where she may remain safely out of the way.' where she may remain safely out of the way.'

The Doctor glowered. 'You're not thinking, thinking, Cadwell! Cadwell!

You're just reacting.'

Cadwell walked slowly over to where the Doctor stood and returned his stare easily. 'Point taken, Doctor. May I suggest that you return to the Adamantium Adamantium with your friend and have your little think, and leave the reacting to us.' with your friend and have your little think, and leave the reacting to us.'

'With pleasure.'

Stoker took the news of Bunny's death badly. The Doctor told her what had happened as gently as he could, but it was a deeply unpleasant task. Lawrence fully expected Stoker to lash out in frustration, but she merely sat down heavily in the armchair in his cabin and stared blankly at nothing.

Lawrence had never seen her so shaken. He poured her some Kalazak brandy but she ignored it. Lawrence settled for simply standing by her as as the Doctor quietly withdrew. the Doctor quietly withdrew.

'I can't believe he's gone,' Stoker said in a whisper. 'Not Bunny. Not Bunny.' Not Bunny.'

Lawrence bit his lip and held out his hand.. He was slightly surprised when she took it, holding it in a tight, cold grip. 'I'm sorry' Lawrence said.

She shook her head, unable to speak. She grasped his hand until her knuckles turned white.

The Doctor draped his frock-coat over Tegan's shoulders as she sat down. She barely noticed. Her head was buried in her hands, and when she looked up her face was streaked with tears. 'Why did it have to be him? Why?'

The Doctor stood awkwardly, not knowing what to say.

'He saved my life,' Tegan said.'He dragged that thing off me, Doctor. And it killed him ...' killed him ...'

'He was a very brave man,' the Doctor said. 'I liked him.'

Tegan wiped her face with a hand, smudging her make-up further. 'Oh, rabbits. rabbits. What about his daughter? He's got a wife and a little girl on Earth waiting for him to come home, Doctor. She's only five or six...' What about his daughter? He's got a wife and a little girl on Earth waiting for him to come home, Doctor. She's only five or six...'

The Doctor looked pained. 'Tegan, I'm so sorry...'

Tegan cried out in anguish, her shoulders shaking as she wept. The Doctor watched her helplessly for a few moments, then turned to leave.

'Doctor?' Tegan sniffed.

He turned to look at her.

'Do whatever you've got to. Stop that thing. Stop it forever.'

The Doctor found Nyssa in the Adamantium's medical bay with Ravus Oldeman. He was lying on one of the treatment couches, wired to a nursing computer.

'I've just heard the news about Bunny,' Nyssa said solemnly. 'Is Tegan all right?'

The Doctor just nodded and stared disapprovingly at the diagnostic readout on Oldeman's computer. 'He's had another dose of neurolectrin! That's the third in as many, as many, hours.' hours.'

'It seems to be having less and less effect,' Nyssa observed. 'It's almost like an addiction.'

'It's exactly like an addiction,' the Doctor said. 'There's no need for it: the dosage must be strictly controlled or the patient will become utterly dependent on it for normal brain function.' He tore the connectors away from Oldeman's forehead with some impatience. 'I knew I should have overseen his treatment personally!'

'Not even you can be everywhere at once,' Nyssa said.

'I sometimes feel I should be.'

'Is there anything I can do to help?'

He looked at her bleakly. 'Perhaps. There's something troubling me about that creature, Nyssa.'

'You mean tracking it down again in the caves?'

'No, that isn't the problem.'

Nyssa was surprised. 'Then what?'

The Doctor tapped his chin thoughtfully for a moment and then said, 'Come with me.'

Stoker wiped her face and said, 'Look at me. Blubbing like a girl.'

'Don't be so hard on yourself,' Lawrence said.'You've had a terrible shock.'

'So many people have died. I can't take it in. I just want to go now, I just want to leave this awful place.'

He squeezed her shoulders gently. 'What about your claim?'

She sniffed. 'Suddenly the mining rights don't seem so important. It's b.l.o.o.d.y ironic: I argued like mad with Bunny to stay on here, to push the claim through, despite everything.

All he wanted to do was go home. I can see his point of view now - only it's too late.'

The Doctor took Nyssa up to the bridge, arriving at the same time as Silas Cadwell. The Consortium man was in a terrible mood. 'Not a trace of that thing anywhere,' he told the Doctor angrily. 'We've scanned the entire cave system, even scoured the place on foot - nothing?'

'It can't have disappeared,' Nyssa said:I know know it hasn't disappeared. It's there somewhere.' it hasn't disappeared. It's there somewhere.'

'Where?' snapped Cadwell. 'And how would you know, anyway?'

'Never mind about that for the moment,' the Doctor said smoothly. 'If we're going to find the Bloodhunter, we have to understand understand it first. No one's stopped to think about what it's doing, what its purpose is.' it first. No one's stopped to think about what it's doing, what its purpose is.'

'It's killing everyone on sight, that's what it's doing.'

The Doctor ignored him.'I've said all along that there's more to this creature than an insatiable thirst for blood. How did it survive for one hundred and sixty years while Ravus Oldeman was in suspended animation, with no food source?

Unless, as I've already surmised, it is genetically predisposed to naturally suspend its own life functions when necessary.'

'That is certainly supported by the evidence so far,'

Nyssa agreed.

'True, but we're still overlooking the most obvious question,' the Doctor said. 'The creature kills, certainly, and without compunction. But how how does it kill its victims?' does it kill its victims?'

'It sucks out all their blood and bile.'

'Why?'

Nyssa shrugged. 'Sustenance? Perhaps it's some kind of vampire?'

The Doctor shook his head. 'No, we already know it survived for one hundred and sixty years without any viable food source. Besides which, the rate of fluid consumption is simply too high: there are roughly eight pints of blood alone in the average human being. The creature isn't physically large, so where's all the blood going? It doesn't require it for its own survival. So why does it require it? 'What's its secret? To put it bluntly, what's it doing doing with all that blood?' with all that blood?'

No one had an answer to that. The Doctor sat and gazed thoughtfully into s.p.a.ce, turning the question over and over in his mind. 'If we can find that out,' he said, 'we will discover exactly what its purpose is.'

Cadwell said, 'Its purpose is to kill.'

'No. Its purpose is to collect blood. The question is - why?'

'This is wasting time,' Cadwell declared. He turned to address one of the crewmen working at a nearby console.

'Well, Jenks, what have you found?'

'Nothing, sir,' Jenks said. 'I've doubled-checked all the readings. I'm sorry, but there isn't a trace of the creature in the cave systems.' Cadwell scowled and bent over the instruments. 'It must must be in the cave system. be in the cave system.

You've made an error - try again.'

'He hasn't made any error,' the Doctor said.

Cadwell turned his scowl on the Doctor, clearly unhappy with the man's habit of contradicting him. The Doctor said, The sensors are functioning perfectly. If the creature was down there you'd have a reading.'

Jenks apologised again and the Doctor clapped him on the back. 'Not your fault. It's just gone into hiding, that's all.'

'Hiding?' Cadwell scoffed. 'Where?'

'Somewhere out of the range of your instruments,' the Doctor replied.'Or somewhere that is shielded from the bio-sensor rays.'

'Such as?'

'Deeper into the cave system, I suspect. That's where the mineral deposits really build up. Bound to interfere with something as delicate as a pa.s.sive bio-sensor beam.'

'It is possible,' Jenks confirmed.

'I know it's possible,' Cadwell snapped. 'So now what do we do?'

'Follow it into the deeper caves,' the Doctor said easily.

This was too much for Cadwell and a thick vein began to throb in his temple. Through gritted teeth he asked, 'And how, precisely, do you plan to do that?'

The Doctor smiled. 'Oh, I think I've got just the thing...'

'Are you sure this is wise, Doctor?' asked Tegan.

The Doctor shrugged on his coat and paused to adjust the sprig of celery on the lapel. But he didn't answer.

Tegan wasn't so easily put off.'Is Nyssa happy with this?'

'Of course she is. Aren't you, Nyssa?'

'Well...' Nyssa began doubtfully.