They ran until they could run no further, when Irisis realised that only Myrum was behind her. Ivar had fallen back and been killed without their even knowing it. Irisis brushed a tear from one eye. He had been just a boy doing his duty.

Myrum was scarlet in the face and labouring under his pack. 'I'd chuck that away, if I were you,' said Irisis.

'I can manage it,' he gasped. 'It's needed. We seem to have lost them.'

Iris doubted that. 'We must have run leagues, Fyn-Mah. Are you sure you're going the right way?'

The perquisitor avoided her eye, staring down the three passages ahead.

'In a straight line,' Irisis went on, 'we'd have gone right across Snizort and out the other side by now.'

Fyn-Mah checked the small object in her hand. 'We go right.'

'You're not leading us out at all!' Irisis said furiously. 'You're taking us further in.'

The perquisitor moved into the right-hand tunnel. 'We had to take the long way round,' she said unconvincingly. 'There's fire in a central core of tunnels surrounding the Great Seep.'

Irisis followed, keeping a careful watch over her shoulder. As she passed what seemed no more than a dark niche in the wall, something slipped out beside them. With a yelp she leapt out of the way, for it looked like a little wingless lyrinx. She had her sword out when it said, in Eiryn Muss's voice, 'This way!'

The disguise was a brilliant one — it might even have fooled a lyrinx, from a distance. Muss was truly a master. How did he create such wonders from the small pack on his back?

'I've found it; he said to Fyn-.Mah. 'The tunnel collapsed and they must've thought it was buried too deep to recover.' He still had that frustrated look 'What's still here?' said Irisis. What were they up to now?

Muss did not answer, but led them past a T-junction down a tunnel littered with fallen rock. The floor drops sharply, just ahead.'

Several slabs of the tunnel had slid downwards, like slices off the end of a hollow loaf. Irisis made it down the half-span onto the first step, and a similar distance to the second, but the third slab had fallen so far that only a crescent-shaped hole, the size of a section through the side of a beer barrel, connected it to the space they stood in. There were smash marks on its upper lip, presumably where the lyrinx had tried to break in.

Irisis hesitated. It would be a tight squeeze. 'If we're halfway through and it slips again, it'll cut us in half.'

'I've been down there,' said Muss. 'It's as safe as anywhere in Snizort.'

'That's comforting!'

Flangers squeezed through head-first, grunting with the effort, his feet waving in the air. Abruptly he cried out and his legs whipped through. Fyn-Mah pulled back, snatching out her knife. Irisis drew her sword — not that it would be much use in such a confined space.

'You damn fool, Muss!' cried an enraged Flangers, following that with a stream of oaths Irisis had never heard before. 'Why didn't you tell me the drop was a span and a half? I nearly broke my neck.'

'I got down it without any trouble,' Muss said indifferently.

'Must be a bloody lizard! Pass me the lantern, Fyn-Mah, and come through carefully. I'll catch you.'

Being small, Fyn-Mah wriggled through without difficulty. Irisis followed. It was a tight fit for her and she felt sure she was going to fell on her head, but Flangers's upstretched hands caught hers and she slid into his arms.

He bore her weight without strain and set her on her feet. Taking up the lantern, he led the way down a series of tunnel slices like thigh-high steps.

'Aren't you going to give Muss a hand?' she said in his ear.

'He can bounce down on his pointy head for all I care.'

'You don't like our prober?'

'There's something a bit off about him; Flangers said out of the corner of his mouth.

Irisis looked back but the spy was already standing at the base of the drop, as if he'd floated down. He brushed past, taking the lantern.

'He's a.strange one,' she said quietly. 'His work is always flawless, but he hasn't a friend in the world, unless you count Flydd. He eats alone, even sleeps alone, if he sleeps at all.'

'Maybe being the perfect spy is all he needs,' said Flangers. 'It's a solitary profession.'

'It's just here!' called Muss. 'Get a move on.'

They crowded into a small, circular chamber whose roof was a perfect dome of sandstone. A squat object like an inverted sombrero stood knee-high on a pedestal in the centre of the room. It had a short brown stalk on which was mounted a yellow frilled brim. It was not alive — it had been created by the lyrinx in one of their patterners.

Fyn-Mah skidded to a stop. 'Myrum, defend the entrance. Muss, check that there's no other way in. Flangers, see if you can get that.'

'There isn't any other way in,' said Muss.

'What is it?' said Flangers.

'It's called a phynadr,' said Fyn-Mah. 'The enemy make them in all shapes and sizes, to draw power from the field. We're taking it back so we can see how it works.'

'The lyrinx tried to break in for it,' said Flangers, 'so it's likely they'll be waiting when we crawl out.'

'Then it it'll be time for you to do your duty, soldier/ said the perquisitor.

Flangers took hold of the object, which slipped through his fingers. 'Can't get a grip on it,' he muttered.

Irisis touched it with her fingers. The phynadr was superficially similar to the torgnadr, or node-drainer, she'd helped Flydd to destroy, though it had been leathery. This phynadr was soft, compressing under her touch but springing back into shape when she let it go.

Flangers put his arms around it and heaved, but his arms slid off. To their right, Fyn-Mah was sketching shapes in the air. Whatever magic it was, Irisis prayed that it would work quickly. She threw a glance over her shoulder.

Flangers whipped out his sword. 'Don't damage it,' yelled Fyn-Mah.

He slid the point of his sword under the flat base of the phynadr. The edges, tinged purple, seemed to recoil from the metal, revealing a white underside. Flangers pushed the sword all the way, levered, and the phynadr popped off, emitting a musky, molasses-sweet odour.

Irisis caught it as it toppled. It was rather heavier than it looked. The phynadr bent in the middle and the base pulled itself down hard, trying to reattach to the pedestal, but Flangers kept the blade underneath. Yellow jelly oozed from beneath the cap. Fyn-Mah pushed Irisis out of the way, drew a black bag over the phynadr and swiftly tied the top. Throwing it over her shoulder, she staggered under the weight, recovered and hurried back to the collapsed section.

'I'll go first,' she said at the vertical wall.

Flangers boosted her up. 'Keep a sharp lookout.'

'Don't worry.' She crawled through. 'It's safe.'

'It would be,' said Irisis. "They want the phynadr more than us, so they'll be waiting around the corner.'

Flangers boosted Myrum, then Irisis. Muss gave Flangers a leg-up. 'Need a hand?' Flangers said.

'I'll be right; said Muss.

'Come on!' Fyn-Mah called. 'It's not far now.'

A lyrinx roared near the T-junction. Myrum shouted a battle cry and ran for it. His sword clacked against a skin plate, something whistled through the air, then he was back-pedalling, attempting to defend himself against two lyrinx at once.

He cursed, slipping to one knee. Irisis was sure he was done for, but the old soldier sprang forward, fast and low, his sword sliding neatly between the belly plates of the leading lyrinx. It sagged to the left, crashing into the other beast, and they went down in a tangle of arms and legs. The soldier dispatched the second with a sword tip to the jugular.

'We go right,' said Fyn-Mah, leading the way with the bag slung over her shoulder.