'It's little wonder it won't quieten,' Coltaine commented, 'with you trying to kill it daily.'

'You've been shouted down by a lapdog, Uncle?' Duiker asked, brows rising.

'Careful, old man,' the scarred Wickan growled.

'Time for you to ride,' Coltaine told Duiker, his eyes lighting on a new arrival. The historian turned to see Nether. She was pale, looking drawn into herself. Raw pain still showed in her dark eyes, but she sat straight in her saddle. Her hands were black, including the flesh under her fingernails, as if dipped in pitch.

Sorrow flooded the historian and he had to look away.

The butterflies rose from the track in a swirling cloud as they reached the forest edge. Horses reared, a few stumbling when struck from behind by those that followed, and what had been a scene of unearthly beauty a moment before now threatened chaos and injury. Then, with the mounts skidding and staggering, jostling, heads tossing, a score of cattle-dogs bolted forward, taking the lead. They plunged into the swarms ahead, the insects rising, parting over the road.

Duiker, spitting out ragged wings that tasted of chalk, caught a momentary glimpse of one of the dogs that made him blink and shake his head in disbelief. No, I didn't see what I thought I saw. Absurd. The animal was the one known as Bent and it seemed to be carrying a four-limbed snag of fur in its mouth.

Order was restored, the dogs managing to clear the path, and the canter resumed. Before long, Duiker found himself settling into the steady cadence. There was nothing of the usual shouting, jests or Wickan riding songs to accompany the thunder of hooves and the eerie whisper of hundreds of thousands of butterfly wings caressing the air above them.

The journey assumed a surreal quality, sliding into a rhythm that seemed timeless, as if beneath and above the noise they rode a river of silence. To either side the bracken and dead trees gave way to stands of young cedars, too few on this side of the river to be called a forest. Of mature trees only stumps remained. The stands became a backdrop against which pale yellow swirled in endless motion, the fluttering filling Duiker's peripheral vision until his head ached.

They rode at the pace of the cattle-dogs, and those animals proved tireless, far fitter than the horses and riders that followed in their wake. Each hour was marked by a rest spell, the mounts slowed to a walk, the last reserves of water offered in wax-sealed hide bags. The dogs waited impatiently.

The trader track provided the Clan's best chance of reaching the crossing first. Korbolo Dom's cavalry would be riding through the thinned cedar stands, though what might slow them more than anything else was the butterflies.

When they had travelled slightly over four leagues, a new sound reached them from the west, a strange susurration that Duiker barely registered at first, until its unnatural irregularity brushed him aware. He nudged his mount forward to gain Nether's side.

Her glance of acknowledgement was furtive. 'A mage rides with them, clearing the way.'

'Then the warrens are no longer contested.'

'Not for three days now, Historian.'

'How is this mage destroying the butterflies? Fire? Wind?'

'No, he simply opens his warren and they vanish within. Note, the time is longer between each effort – the man tires.'

'Well, that's good.'

She nodded.

'Will we reach the crossing before them?'

'I believe so.'

A short while later they came to a second cleared verge. Beyond it, rock pushed up from the earth to the east and west, creating a ragged line against the insect-filled sky. Directly ahead, the track began a downward slope along the path of a pebble-filled moraine, and at its base was a broad clearing, beyond which was revealed a flattened yellow carpet of butterflies that moved in a mass eastward.

The River Vathar. The funeral procession of drowned insects, down to the sea.

The crossing itself was marked by twin lines of wooden poles spanning the river, each pole bearing tied rags, like the faded standards of a drowned army. On the eastern downstream side, just beyond the poles, a large ship rested at anchor, bow into the current.

The breath hissed from Nether upon seeing it, and Duiker felt his own tremble of disquiet.

The ship had been burned, scorched in fire from one end to the other, making it entirely black, and not a single butterfly had alighted on it. The sweeps of oars – many snapped – jutted in disarray from the craft's flanks; those with blades were dipped into the current and dead insects adhered to them in lumps.

The Clan rode down towards the open flat that marked this side of the crossing. A sailcloth awning stood on poles near a small hearth which smouldered with foul smoke. Beneath the makeshift tent sat three men.