Every passing refugee – and there were more every day – heightened Aviel’s fears for her own future. They staggered into Casyme with nothing more than they could carry on their backs, and she had never seen such beaten people. Their eyes were hollow, their clothes dirty, and none looked as though they had eaten a decent meal in a week. Snoat’s armies were stripping the land of everything that had value.

Yet he was a minor problem compared to the Merdrun. What would happen when they invaded? Mass hysteria? A complete breakdown of civilisation, in which people like herself would be the first victims?

She tightened the clamps on her smallest still. She was distilling lavender oil now and it was a laborious process – a bucket of lavender, after hours of distillation, produced less than half a teaspoon of oil. But what use was lavender oil in a world at war?

After bringing her home yesterday Shand had sent out all his message skeets then raced off to Chanthed, saying he would not be back for at least six weeks. He had taken the little phial of perfume Aviel had blended for Wilm to remind him of home, but had forgotten his promise to teach her the first lessons in scent potion making.

She knew no more than he had told her on the ride home: Mancery works by mentally locating a source of power, finding a way to draw some of that power safely, focusing it to the purpose in hand, then releasing it.

Power either came from within or was drawn from an enchanted device. And using mancery came at a cost: aftersickness. But if a mancer was reckless like Shand’s late master, Radizer, or unskilled or just unlucky – both of which applied to her in spades – the cost was liable to be a painful or gruesome death.

She could not imagine what an inner source of power was, though surely it had to do with willpower, determination and focus, all things she had in abundance. And Shand had said she had a gift for scent potions. Dare she try by herself?

How had she made that accidental potion that had so disabled him three years ago? Aviel lit a candle and sat up in bed with her journal, reading what she had done that day. Where had she found power to turn a cleansing blend of perfumes into a laxative scent potion?

She had been standing at her bench when the room around her faded into darkness and an image had slowly come into focus. Aviel relived the moment. She was looking into a well, narrow but deep, and the water was so far down that she could only make out the faintest reflection. Though it did not look like water; it had an oily appearance. She mentally reached down to it, stretching as far as she could reach, then further, further. Her arm seemed to elongate; it really hurt. She scooped up some of the liquid in a cupped hand and brought it back up, the liquid dripping through her fingers.

Her hand was empty, the liquid gone save for an oily, glistening wetness. She rubbed her forehead with her damp fingers, smelled the scent blend she had made that day – jasmine, cedar, hints of woodsmoke, citrus, sage and other things – and light exploded behind her eyes.

Aviel roused herself. She was in her bed and her head was throbbing, as it had after she’d made the laxative scent potion, though she still did not know what she had done. Was the well some inner source of power? She could not guess; she needed Shand’s primer.

She lit a lantern and splashed up the track to the house. Perhaps he’d left her a note. He sometimes did when he went away in a hurry. It was raining heavily now, cold and depressing. She unlocked the back door and went inside. The air was stale and the house felt abandoned. The scrubbed kitchen table was empty, and so was the bench. He hadn’t left her anything.

The cold heightened the ever-present pain in her ankle. She sat down at the table. What to do? She heard a faint drumming, the summon stone working its evil on the land, and shuddered.

Shand would be furious if she searched his house for the primer, but the invasion could occur before he returned and she had to protect herself. Her only hope was to start learning about scent potions right away.

She started at the back of the house and worked forward. The bookcase by the main fireplace held dozens of handwritten books, mostly volumes of the Histories and copies of several of the Great Tales, but also a book of epic poems, a bestiary that had been read so many times the pages were coming out, and an atlas with a series of blank pages at the end entitled The Unknown Lands.

She went up the long staircase, which made a right-angle bend halfway up. There were four rooms upstairs, plus the observatory under its little dome. It was furnished with a stool, a squat mirror telescope and an almanack in which he had entered astronomical readings over a period of years. Aviel sat on the stool, idly turning the pages. She had not seen any mention of the Secret Art, though he would hardly leave such valuable and dangerous books out in the open.

Shand had lived for hundreds of years, his life extended by a gift from his lover, Yalkara, who had subsequently rejected him. Therefore the primer, which he had used as an apprentice, must also be ancient, and ancient books had a particular smell.

The rain grew heavier; it was pounding down now. She limped down the stairs. He must have a secret hiding place, probably protected by a spell or charm so it could not be seen. But would he have thought to protect his hiding place against a book’s smell?

Aviel went back and forth, sniffing. Nothing downstairs and nothing upstairs. What about the cellar? A musty smell led her to a trapdoor in the far corner of the living room under the little round rug, and a ladder ran down for fifteen rungs. She winced her way down it into a cavern hewn out of layered yellow and brown rock. There were puddles of seepage on the floor and a mouldy smell. Beads of moisture on the far wall glistened red and orange in the lantern light.

Behind her a series of iron racks contained dusty bottles and stoppered glass flasks, a dozen ten-gallon barrels of wine, and six small barrels of the raw spirit Shand used for making brandies and liqueurs. But there was no smell of old books.

Until she sniffed along the wine barrels, and the one in the far corner had the faintest aroma of aged parchment. She hesitated. This was wrong; Shand would be apoplectic.

She found a hidden catch at the back and opened the barrel. Inside, wrapped in canvas and then in layers of waxed paper, was a book, eleven inches square, with covers of pink polished rosewood inlaid with camphor laurel, sandalwood, incense cedar and other scented timbers. It contained several hundred pages of fine cream-coloured parchment, though many of the pages were stained, some smelled bad, and the combination of odours made her nose prickle. But it wasn’t Shand’s primer – the name on the cover was Radizer and the title was Scent Potions.

Shivers crept up the outsides of Aviel’s thighs. This was the grimoire of Shand’s reckless master, who had blown himself to bits while trying to make one of the potions. It was a deadly book, one no apprentice would be allowed to open save under the supervision of her master. Yet she, who had never done anything really reckless in her life, was thinking about using it by herself.

If she began there would be no going back. No regaining Shand’s trust either, and after all he had done for her she could not so betray him. She replaced the grimoire in the barrel and was splashing down through the puddles to her workshop when she heard the crack of huge wings and a furious shriek from the direction of the skeet house.

Not again! She got a fist-sized piece of rabbit, headed to the skeet house and, with some difficulty, removed the red-cased message. Aviel opened it in the workshop, hunched up against her brazier.

The brazier gave out no heat. Aviel’s feet and hands felt as though they had turned to ice.

Our very existence is in peril… every second counts. Destroy the stone… not mage fire.

Why not?

Even if she could find someone who knew how to direct a skeet to Chanthed, Shand would not get there for the best part of a week. But the summon stone had to be found urgently and if seconds counted, a week was out of the question.

Aviel was forced to a terrible conclusion. It was up to her to locate the summon stone right away so, when Shand got the message, he could destroy it.

But to do that, she would need his grimoire.