Karan was sitting on her horse, staring into nowhere, when Shand and Ussarine rode up.

“I’ve lost Llian and Wilm’s tracks,” Shand said. “I suspect they’ve gone east but we’ve got to be sure. Come on.”

“Can’t think about anything but Sulien,” said Karan. “I’ll catch you up.”

He gave her a cold stare, then rode off. Good riddance! She was fed up with his suspicions and accusations.

“Don’t do anything rash,” Ussarine said softly, and followed.

Karan made a mug of herb tea, using the aromatic leaves of a twisted little mint bush, sat with her back to the trunk of a small tree and focused on her breathing, in and out, trying to eliminate everything from her mind. In and out.

But she kept seeing Sulien’s tormented face as she’d offered to go with the Whelm. Why had she allowed her to do it? The thought of gentle Sulien being punished, starved and made into a little Whelm was unbearable.

Karan had to know she was safe but a link was out of the question. This left only one possibility, one she prayed the magiz would not be able to detect. She unlocked the little box and studied the lump of hrux inside. The smell did not seem as bad as the last batch. She cut off a small piece, then decided she needed more, to be sure.

No, that was the hrux talking. A smaller piece, not a larger one. Her hand had a tremor and her pulse was racing. She really wanted it, and the urge had to be resisted every time. She fought it until it faded, cut off a tiny piece, locked the box and put the piece in her mouth. Karan went to lick the knife – no, resist it always.

Her surroundings vanished as if she had been thrown through a hole into another land. She tried to focus on a mental image of Sulien but saw Unick instead.

He was staggering down a winding mountain track, gasping and grunting, brandishing his bloody fists at the sky and crying out for the source that was now lost to him. Its loss was eating him alive.

You bloody bastard, Llian! he cried. I’ll smash you to bits, you bloody, bloody bastard.

Unick took a little circle of glass from his pocket and sniffed it. He turned left and right, his shrunken eyes jerking around in sockets too big for them. You too, you little bitch. I’m not letting you ruin it. Karan shrank back, only to realise that he was not talking about her.

It was all she saw of him, thankfully, and she must have slept, for she suddenly realised that she was sagging forward, her hair sweeping the ground. She sat up, surprised that she was not suffering the after-effects of hrux.

What news from our new world? said a familiar voice, Gergrig’s.

Mist cleared and she saw a steep slope sheathed in crevassed blue ice. It was more than half a mile higher than the place where she had destroyed the magiz’s leg; the wall of the bulbous ice fortress that guarded the flat mountaintop and the great Crimson Gate was only a few hundred yards above her.

Gergrig and a big man with a flattened nose and a rounded metal plate where the top left side of his head should have been were standing around a roaring fire fuelled with chunks of black oily rock. The mountainside was dotted with such fires, and the smoke curling up from them had collected in every hollow, making brown pools in the blue-white.

Between the two men, the magiz, swathed in grey furs, was perched on a rock ledge while an attendant strapped a mechanical leg, made of black iron and shiny brass, onto her stump.

The magiz looked up at Gergrig. Her thin face was gashed by pain lines but she seemed happy. The fools don’t even know I’ve a spy in their midst, she said. Not even the spy knows. She laughed mirthlessly.

What do they know? said the man with the plate in his head.

They think the drumming is causing all their troubles, sneered the magiz. They don’t realise I’m pulling their strings.

Even the man called Snoat?

Especially him. He’s my greatest work of art. I’ve even convinced him that the summon stone, and ourselves, are a fantasy. She let out a revolting, snorting giggle.

There are two strings you’re not pulling, Gergrig said, looking pointedly at her mechanical leg. The mother’s and the daughter’s.

They’re both at breaking point. And the moment either cracks, I’ll drink both their lives!

Karan snapped the connection and sat there, mouth dry and heart pounding. The moment either cracks meant that Sulien was also vulnerable, and there was not a thing Karan could do about it.

“Karan?” Shand was shaking her.

Her head was throbbing, one of the after-effects of hrux. Another was weakness in her limbs. Her legs and arms were trembling and her mouth was so dry she could not speak.

“Don’t tell me!” Shand said sharply. “Not again!”

“What’s the matter?” said Ussarine.

“The damn fool has taken hrux. Karan. Karan!”

“Water,” she croaked.

Ussarine pressed the spout of a water skin through her lips and squeezed it. Warm water spurted in. Karan rinsed it around her mouth and swallowed. “I’m all right. Help me up.”

Shand and Ussarine came into focus. “Did you find Llian’s tracks?” said Karan.

“Heading east. Why hrux, Karan? You know how dangerous —”

“There was no other way.”

“What did you see?”

Her memories were jumbled up and it was a struggle to put them in order. “Unick! East of Tullin. He sniffed a little circle of glass and said, ‘You too, you little bitch. I’m not letting you ruin it.’”

“A little circle of glass?”

“Like the neck of a tiny bottle.”

“Or a perfume phial,” Shand said grimly. “Aviel asked me to give it to Wilm but I broke it outside Unick’s workshop. And like a damn fool, I left it there.”

“I don’t see —” said Karan.

“She accidentally made another scent potion; I smelled it and it linked me to her. It must have affected Unick the same way.”

Karan’s skin crawled. “And he’s terrified Aviel will find the source.”

“The summon stone,” said Shand. “We’ve got to go.”

“There’s more,” said Karan. She told them what the magiz had said.

“An unwitting spy.” He studied her calculatingly. “Who?”

“The magiz didn’t say.” Could Karan herself be the spy, betraying the allies through the magiz’s stigma? No, the idea was absurd. Then who? She had no way of finding out without going back to Cinnabar, and she wasn’t going to do that.

“Can we get to Casyme before Unick does?” said Ussarine.

“It’ll be touch and go,” said Shand.

They raced after Llian and Wilm, riding all the hours of daylight and whenever there was enough moonlight to see, only sleeping three or four hours a night. But Llian and Wilm must have been going just as hard and they did not catch them.

Karan’s terror grew with every step, for she kept picking up flashes of incoherent fury that could only be coming from Unick. Llian would not last a minute in a fight with him.

After four of the hardest days’ riding in her experience they reached Casyme in the evening, but they were too late. The lock on Aviel’s workshop was broken and she was gone.

“No sign of a body, at least,” Ussarine said bleakly.

“Maybe he took her with him,” said Shand.

“Hello,” said Karan, smiling at a grubby, yellow-haired boy who had appeared out of the darkness.

He made wild movements with his hands. He was clearly terrified.

“My stable boy, Demoy,” said Shand. “He’s mute.”

He squatted down in front of the lad and they exchanged signs for a minute or two. Shand shook Demoy’s hand and gave him a silver coin. Demoy took their horses into the stables.

“Unick came through around midday,” said Shand, “hunting Aviel. When he found she was gone he broke into my house, then stole my best horse and went after her.”

“Where did she go?” said Karan.

“Demoy doesn’t know. But she left in the night, in a tearing hurry.”

“What about Llian and Wilm?”

“The lad’s been hiding ever since Unick left. Doesn’t know anything about them.”

“So we don’t know if they’re ahead or behind us.”

“No. Come into the house.”

Karan was so tired that she was starting to hallucinate and she dared not risk that; visions could link her to Sulien or even take her back to Cinnabar. The house was undisturbed apart from the cellar, from which Unick had stolen several flasks and two little barrels of raw spirit.

“The bastard must be able to smell liquor,” said Shand.

“Lucky he didn’t tear the place apart.”

“He’s in too much of a hurry. Come into the kitchen when you’re ready.” He indicated the washroom. “There won’t be any bread but the larder is full.”

Karan washed her face and hands and went into the kitchen. The old table was piled with sausages, cheeses, dried fruit and jars of pickled vegetables. Shand was studying a sheet of paper, a letter from Malien.

“It’s weeks old,” he said. “Must have come after I left for Chanthed. It doesn’t tell me anything new.”

But below it was written in a hasty scrawl, “Gone after it, Aviel.” She had sketched a tower which, though crudely drawn, drove thorns into Karan’s backbone. The drumming sounded in her inner ear, long and low.

“Carcharon,” said Shand. “I might have known.” He gave Karan a very cold glance. “We’re coming to the point where you have to make up for what your ancestors did up there.”

“What… do you mean?” whispered Karan.

“You’ve got to go back to Cinnabar and do the job properly.”

“It’s like the South Pole up that mountain. In what I’m wearing I wouldn’t survive five minutes.”

He stalked out, shortly returning with a down-filled coat, hood and trousers, and a pair of fur-lined boots. “Take these.”

“Shand,” said Ussarine, “I don’t think —”

“Who asked you?” Shand snapped. “Karan’s ancestors corrupted Carcharon, weakened the barrier between the world and the void, let savage creatures through… and may even have allowed the summon stone through in the first place.”

His words were a series of hammer blows. Could her father’s work have allowed the summon stone into Santhenar? She could not bear to think about it – it tainted every memory she had of him.

Shand was packing the food when an awful thought occurred to him; Karan saw it in his leathery face. “Aviel has never been anywhere near Carcharon. How could she know what it looks like?”

He ran into the main room; a trapdoor crashed open and Karan heard him thumping down a ladder.

“What’s going on?” said Ussarine.

“I don’t know.” Karan was numb, incapable of thought. She stuffed the cold-weather gear into her pack. Not Cinnabar again; it was a death sentence.

Shand reappeared, panting. “The little cow!” he said, part furious and part impressed, and raced down to the workshop. Karan and Ussarine followed. He sniffed various jars and flasks, then said, “She’s taken my grimoire – and used it.”

“Wouldn’t that be dangerous?” said Karan.

He shivered and rubbed his forearms. “There’s only one scent potion Aviel could have used to locate the summon stone, and it’s one of the most deadly in the grimoire. I wouldn’t even be game to make the Eureka Graveolence.”

“She must be a remarkable woman,” said Ussarine.

“Aviel is undoubtedly remarkable but she’s not a woman. She’s a girl, not yet sixteen, who’s afflicted with very bad luck.”

“She’s already used the scent potion successfully,” said Karan.

“To locate the stone she’ll have to keep using it, and the more she does the worse its effects will get. And the greater the risk that it will be fatal.”