tens of metres, and Clavain was unable to decide whether it was some weird natural feature — carved, perhaps, by a hot sub-glacial river — or whether it had been dug by hand, much more recently. The walls were veined with worm tracks: a marbling like an immense magnification of the human retina. Here and there Clavain saw the dark smudges of worms moving through cracks that were very close to the surface, though he knew it would be necessary to stare at them for long seconds before any movement was discernible. He groaned, the stooping becoming painful, and then the tunnel widened out dramatically. He realised that he had emerged into a much larger space.
It was still underground, although the ceiling glowed with the blue translucence of filtered daylight. The covering of ice could not have been more than a metre or two thick; a thin shell stretched like a dome over tens of metres of yawing nothing. Nearly sheer walls of delicately patterned ice rose up from a level, footprint-dappled floor.
‘Ah,’ said Iverson, who was standing near one wall of the chamber. ‘You decided to join us.’
Clavain felt a stab of relief seeing that Felka was standing not far from him, next to a piece of equipment Clavain failed to recognise. Felka appeared unharmed. She turned towards him, the peculiar play of light and shade on her helmeted face making her look older than she was.
‘Nevil,’ he heard Felka say. ‘Hello.’
He crossed the ice, fearful that the whole marvellous edifice was about to come crashing down on them all.
‘Why did you bring her here, Iverson?’
‘There’s something I wanted to show her. Something I knew she’d like, even more than the other things.’ He turned to the smaller figure near him. ‘Isn’t that right, Felka?’
‘Yes.’
‘And do you like it?’
Her answer was matter of fact, but it was closer to conversation than anything Clavain had ever heard from her lips.
‘Yes. I do like it.’
Galiana stepped ahead of him and extended a hand to the girl. ‘Felka? I’m glad you like this place. I like it, too. But now it’s time to come back home.’
Clavain steeled himself for an argument, some kind of show-down between the two women, but to his immense relief Felka walked casually towards Galiana.
‘I’ll take her back to the rover,’ Galiana said. ‘I want to make sure she hasn’t had any problems breathing with that old suit on.’
A transparent lie, but it would suffice.
Then she spoke to Clavain. It was a tiny thing, almost inconsequential, but she placed it directly in his head.
And he understood what he would have to do.
When they were alone, Clavain said, ‘You killed him.’
‘Setterholm?’
‘No. You couldn’t have killed Setterholm because you are Setterholm. ’ Clavain looked up, the arc of his helmet light tracing the filamentary patterning until it became too tiny to resolve; blurring into an indistinct haze of detail that curved over into the ceiling itself. It was like admiring a staggeringly ornate fresco.
‘Nevil — do me a favour? Check the settings on your suit, in case you’re not getting enough oxygen.’
‘There’s nothing wrong with my suit.’ Clavain smiled, the irony of it all delicious. ‘In fact, it was the suit that tipped me off. When you pushed Iverson into the crevasse, his helmet came off. That couldn’t have happened unless it wasn’t fixed on properly in the first place — and
Setterholm — he was sure the man was Setterholm — snorted derisively, but Clavain continued speaking.
‘Here’s my stab at what happened, for what it’s worth. You needed to swap identities with Iverson because Iverson had no obvious motive for murdering the others, whereas Setterholm certainly did.’
‘And I don’t suppose you have any idea what that motive might have been?’
‘Give me time; I’ll get there eventually. Let’s just deal with the lone murder first. Changing the electronic records was easy enough — you could even swap Iverson’s picture and medical data for your own — but that was only part of it. You also needed to get Iverson into your clothes and suit, so that we’d assume the body in the crevasse belonged to you, Setterholm. I don’t know exactly how you did it.’
‘Then perhaps—’
Clavain carried on. ‘But my guess is you let him catch a dose of the bug you let loose in the main base — Pfiesteria, wasn’t it? — then followed him when he went walking outside. You jumped him, knocked him down on the ice and got him out of his suit and into yours. He was probably unconscious by then, I suppose. But then he must have started coming round, or you panicked for another reason. You jammed the helmet on and pushed him into the crevasse. Maybe if all that had happened was his helmet coming off, I wouldn’t have dwelled on it. But he wasn’t dead, and he lived long enough to scratch a message in the ice. I thought it concerned his murderer, but I was wrong. He was trying to tell me who he was. Not Setterholm, but Iverson.’
‘Nice theory.’ Setterholm glanced down at a display screen in the back of the machine squatting next to him. Mounted on a tripod, it resembled a huge pair of binoculars, pointed with a slight elevation towards one wall of the chamber.
‘Sometimes a theory’s all you need. That’s quite a toy you’ve got there, by the way. What is it, some kind of ground-penetrating radar?’
Setterholm brushed aside the question. ‘If I was him — why would I have done it? Just because I was interested in the ice-worms? ’
‘It’s simple,’ Clavain said, hoping the uncertainty he felt was not apparent in his voice. ‘The others weren’t as convinced as you were of the worms’ significance. Only you saw them for what they were.’ He was treading carefully here; masking his ignorance of Setterholm’s deeper motives by playing on the man’s vanity.
‘Clever of me if I did.’
‘Oh, yes. I wouldn’t doubt that at all. And it must have driven you to distraction, that you could see what the others couldn’t. Naturally, you wanted to protect the worms, when you saw them under threat.’
‘Sorry, Nevil, but you’re going to have to try a lot harder than that.’ He paused and patted the machine’s matt-silver casing, clearly unable to pretend that he did not know what it was. ‘It’s radar, yes. It can probe the interior of the glacier with sub-centimetre resolution, to a depth of several tens of metres.’
‘Which would be rather useful if you wanted to study the worms.’
Setterholm shrugged. ‘I suppose so. A climatologist interested in glacial flow might also have use for the information.’
‘Like Iverson?’ Clavain took a step closer to Setterholm and the radar equipment. He could see the display more clearly now: a fibrous tangle of mainly green lines slowly spinning in space, with a denser structure traced out in red near its heart. ‘Like the man you killed?’
‘I told you, I’m Iverson.’
Clavain stepped towards him with the ice pick held double-handed, but when he was a few metres from the man he veered past and made his way to the wall. Setterholm had flinched, but he had not seemed unduly worried that Clavain was about to try to hurt him.
‘I’ll be frank with you,’ Clavain said, raising the pick. ‘I don’t really understand what it is about the worms.’
‘What are you going to do?’
‘This.’
Clavain smashed the pick against the wall as hard as he was able. It was enough: a layer of ice fractured noisily away, sliding down like a miniature avalanche to land in pieces at his feet; each fist-sized shard was veined with worm trails.
‘Stop,’ Setterholm said.
‘Why? What do you care, if you’re not interested in the worms?’
