The splash came again. This time, both warriors gasped. ‘What is that?’ cried the second one.

Hylas heard Pirra breathe in with a hiss. She was staring at the disc of moonlit Sea beyond the cave mouth. Then he saw it too: a dolphin arching out of the Sea, spouting glittering jets of light as it raced towards them down the path of the Moon.

Nearer and nearer it sped. With a catch at his heart, Hylas saw its sleek silver back and the scars on its nose. He watched it swerve in front of them and make a great shining leap, crashing down and sending a large wave drenching the headland where the warriors were standing.

For a heartbeat, as Spirit arched once more out of the water, his large dark eye met Hylas’. Thank you, my friend, Hylas told him silently. Then the dolphin was gone.

The water rocked. Spirit did not reappear.

Seawater was raining from the rim of the overhang, and the warriors were spluttering. ‘That’s what you heard,’ growled the first one. ‘A dolphin! Let’s get out of here!’

‘How was I s’pposed to know?’ snapped the sneering one, who was sneering no longer. ‘Anyway, it better not come back!’

Sounds of a scuffle. ‘Put that spear down! Don’t you know dolphins are sacred?’

‘All right, all right! Let’s go. We’re too close to the marshes, and those Dwellers come and go like ghosts …’ Their voices faded as they trudged up the slope.

‘Thank you, Spirit,’ murmured Pirra.

Hylas didn’t reply. He longed for the dolphin to come again; but something told him that Spirit was already far away, swimming out to Sea to rejoin his pod.

The jellyfish had gone as swiftly as they’d come, leaving stinging blisters on Hylas’ shoulders and chest. Pirra was wincing and rubbing her arms. ‘Somehow I don’t fancy climbing that headland any more,’ she muttered.

‘Nor me. We’ll have to get back in the boat and take our chances up the coast.’

Which way? East of the headland, the coast was directly overlooked by the Crows. ‘But if we go west,’ said Pirra, ‘how do we avoid the marshes?’

‘The captain said there’s a stream between them and the headland. If we can find it, we can follow it inland –’

‘If,’ she said.

After the chill of the cave, it was a relief to get out into the hot autumn night. The moonlight was so bright it made them blink, but a bank of white mist had crept in, and hid the coast from view.

When they’d dragged the boat from beneath the overhang, Pirra took the oars, and Hylas stayed in the water, swimming with one hand on the prow. To find the stream, he was going to try a trick he’d learnt from Periphas, the ex-slave who’d been his friend after they’d escaped Thalakrea.

‘Fresh water feels colder than the Sea,’ he explained to Pirra. ‘With luck, I can find the stream by feel.’

He was also hoping against hope that Spirit might return. But as they started off, with Pirra quietly rowing and he swimming one-handed, guiding them as close to the rocks as he dared, he saw no gleaming grey back and felt no smooth dolphin snout lightly caressing his flank. Only a shoal of small silvery fishes kept him company, swarming and flickering around his legs. Spirit wouldn’t come again. He could feel it.

He began to lose heart. What are we doing here? he thought bitterly. The Crows have the dagger. We don’t even know where it is. And for all I know, Issi might be long dead.

In the two years she’d been missing, he’d tried not to think of her, it hurt too much; but now that he was back, it was harder to keep the memories at bay. She kept butting into his thoughts: his noisy, argumentative, infuriating little sister …

In the boat, Pirra gave a convulsive shudder. ‘Something’s wrong,’ she hissed.

Now Hylas felt it too. It wasn’t the stabbing headaches, the sickness and flashing lights that he got before a vision; it was dread, pressing on his heart like a hand.

Echo lit on to Pirra’s shoulder, and she put up one hand and touched the falcon’s foot. Echo sat hunched, with her head sunk in her shoulders. Pirra frowned.

‘What’s wrong with her?’ breathed Hylas.

‘I don’t know,’ she whispered. ‘It feels as if – as if she’s scared.’

‘Echo? She’s not scared of anything! Except ants.’

‘I know. But I feel it too.’

Suddenly, the fish around Hylas fled in a silent silver explosion, and for an instant, something cut across the Moon. It was moving too fast for him to see if it was bird or cloud, but it was huge, and as the light briefly died, dread rushed through him like a dark wind.

The thing in the Sky was gone as swiftly as it had come, and once again, the Moon shone bright. Neither Hylas nor Pirra spoke. They didn’t want to voice their suspicions out loud, but both were thinking of the Angry Ones: the terrible spirits of air and darkness who were worshipped by the Crows.

As they moved forwards, Hylas felt the water turn abruptly colder. ‘I think we’ve found that stream,’ he murmured.

‘It can’t be!’ whispered Pirra. ‘These are the marshes!’

Through shifting veils of fog, the stream showed as a strip of dull silver, flanked by man-high reeds with dry brown heads that exhaled a swampy breath of decay. Here and there, a low hunched willow appeared in the mist, or a tall poplar, standing guard. One of the poplars had died and fallen across the mouth of the stream. In its white skeletal branches, three black cormorants roosted with their heads beneath their wings.

‘We can’t go in there,’ said Pirra. Even the throbbing ring of night crickets and the low eep-eep of frogs sounded a warning.

Ahead of them, the reeds stirred – and Havoc appeared, with a large fish wriggling in her jaws. The lioness cast a casual glance at Hylas and Pirra, then leapt on to the dead tree trunk – waking the cormorants, who flew off into the mist – and sprawled full length, with her hind legs dangling on either side of the trunk. With the fish grasped firmly between her forepaws, she started noisily crunching it up.

Hylas breathed out. ‘She doesn’t seem too worried.’

‘Of course not,’ snapped Pirra, ‘she’s a lion!’

Hauling himself into the boat, he wrung out his long fair hair. ‘Well I think we’ll have to risk it. After all, the captain said the Marsh Dwellers are Outsiders, like me –’

‘And how will you get a chance to tell them who you are?’ demanded Pirra. ‘The captain also said they shoot on sight!’

‘Pirra, we can’t go back, and for all we know, these marshes stretch right along the coast! Have you got a better idea?’

They’d left the boat tied to the skeleton tree, but they were finding it hard to follow the stream, as the reeds didn’t want to let them through. They were dense and tussocky, except where they opened without warning on to treacherous, sucking pools of mud.

Havoc, having finished her meal, fared better, as her large paws prevented her from sinking; but she stayed close to Hylas, now and then glancing up at him with big Moon-silvered eyes: Are you sure about this?

‘Did you see that?’ whispered Pirra suddenly.

‘What? Where?’

‘I saw lights, but they went out … Over there!’

A dim blue glimmer on the other side of the stream. Hylas had no sooner spotted it, than it blinked out.

‘Let’s go back,’ said Pirra beside him.

‘And go where? If we can just follow this stream, it’s bound to lead us out of the marshes –’

‘If we get that far. If the Marsh Dwellers don’t –’ With a cry, she lurched against him.

The Crow helmet had been spiked on a fishing spear jammed into a tussock: Pirra had nearly walked right into it. The only trace of the helmet’s former owner was a hank of long black warrior braids that had been roughly knotted to its crest. From the other end of these dangled a large, ragged flap of bloody scalp.

‘Now can we go back?’ muttered Pirra. ‘You don’t have to be a Marsh Dweller to know that this means Keep Out!’

‘But they meant it for the Crows, not us –’

‘And you’re quite certain of that, are you?’

After a brief, fierce argument which Pirra won, they started back for the skeleton tree; but when its white limbs loomed out of the mist, Hylas halted. ‘We can’t go back,’ he said in an altered voice. ‘The boat’s gone.’

Pirra stared at him blankly. ‘But you tied it up, I saw you.’

He licked his lips. ‘The Marsh Dwellers are Outsiders, Pirra. We won’t see them unless they want us to.’

Now they had no option but to follow the stream inland.

They hadn’t gone far when it narrowed and became nothing more than a willow-choked creek. Hylas felt eyes on him. ‘Stay close,’ he murmured. ‘They’re all around, I can feel them.’

Out loud, he called softly: ‘I’m an Outsider, too. I come from Mount Lykas, in Lykonia, but my mother was a Marsh Dweller from Messenia. Like you.’

No reply. A faint night breeze stirred the reeds and rattled their dry brown heads. The frogs and the night crickets had fallen silent.

‘I’m looking for my sister,’ Hylas went on. ‘She went missing two summers ago when the Crows attacked our camp. Her name is Issi. I think that means “frog” in your speech.’

Havoc emerged from the mist, making them start. Fish scales glinted on her muzzle and in her chin fur. Rubbing her wet head against Hylas’ thigh, she stood and stared into the mist.

Pirra touched his wrist. Her dark eyes were wide in her pale, pointed face. ‘Don’t call again. I don’t think they like it.’

Havoc raised her head and snuffed the air. Her tail was taut: she’d sensed something upstream.

At that moment, lights flashed behind Hylas’ eyes and a burning finger stabbed his temple. He doubled up, clutching his head.

‘Hylas!’ hissed Pirra. ‘Is it a vision?’

He tried to answer, but no words came. Everything around him was suddenly sharper and more vivid. He saw the swampy green smell rising from the reeds. He heard the suck of a frog’s small, sticky feet as it clambered up a stem. And in the midstream, where Pirra saw only weeds, he saw a water spirit rising before him.

At first, she was a nebulous thing of mist and moonlight, but as she rose higher, pearly flakes of light coalesced until she was as clear as the reeds around her. Her green hair floated like weeds, and her cold white eyes slid past Pirra, lingered briefly on Havoc – and pierced Hylas’ gaze.

With a grey snarl of a smile, she stretched one long, dripping arm towards him, and held out her hand. On her glistening palm sat a tiny tree frog, black in the moonlight. With the other hand, the spirit pointed upstream.

Hylas glanced from the tiny black frog to the radiant webbing between the thin, pointing fingers and in a flash, the spirit’s meaning burst upon him. Frog. Issi. In the marshes.

He forgot the threat from the Marsh Dwellers. ‘She’s in there!’ he cried, crashing through the reeds. ‘Issi’s in the marshes!’

‘Hylas come back!’ shouted Pirra.

He ignored her, squelching upstream with Havoc in his wake.

Something grabbed his ankle and yanked him into the air, he found himself swinging over the stream by one leg. He was caught in some kind of net.

But the net had also snagged one of Havoc’s forepaws, and with a snarl the lioness lashed out with her dagger-sharp claws, ripping apart the tough webbing as if it was gossamer, and dropping Hylas into the stream with a splash.

He surfaced, spitting out waterweed. Havoc had already bounded off into the reeds.

Frightened and furious, Pirra came floundering towards him. ‘What were you thinking? You could have been killed!’

Too ashamed to speak, Hylas scrambled on to the bank and hacked at the trip rope round his ankle. It was made of fishskin: thin, but tough. Above him, the sapling, which had been bent double when the trap was set, was now swaying, with the torn net trailing from its crown.

The water spirit had vanished. Frogs eep-eeped mockingly. Reeds rattled with harsh laughter. Pirra was right. If that trap had been spring-loaded with a spear instead of a net, either he or Havoc would be dead by now.

And the marshlights were back, a flickering blue ring all around them – although still there was no one in sight.

Hylas’ hand went to his wedjat amulet. ‘Keep your knife sheathed,’ he told Pirra softly, as they stood back to back.

‘I haven’t drawn it,’ she replied. No point. Knives would only make things worse.

‘I’m from the mountains of Lykonia,’ Hylas called to the wavering ring of lights. ‘But my mother was a Marsh Dweller, like you!’

Silence. But the lights began to close in.

Hylas held up his hands, palm outwards in friendship. ‘I’m looking for my sister. Her name is Issi. She went missing when the Crows –’

The lights blinked out. A fishing spear skewered the mud a hair’s breadth from Hylas’ foot. He forced himself to keep still. Pirra sucked in her breath, but stood her ground.

A voice spoke from the reeds in a harsh, guttural accent. ‘We heard you the first time. Stranger.’