Anna knew what they were as soon as she saw them. Twin Jeunet Carot engine pods, all the way from Paris. Her parents’ ship had been powered by pods like those. Anna’s father had always said they were the best aero-engines ever built. They had carried the Aerial Merchant Vessel Mermaid uncomplainingly along the Bird Roads for the whole of Anna’s childhood, and it had not been the pods’ fault when the wind changed unexpectedly above the Tannhäuser Mountains one day and they were choked with the fine ash from a volcano.

Even then, they could have been fixed. Anna’s parents had steered the ship safely down on to a little traction town with a good air harbour and set to work, but before they could finish the repairs a storm swept down on the town, and in the heart of the storm came Arkangel, the Hammer of the High Ice, the greatest predator-city of the north.

Anna had caught one dreadful glimpse into the city’s furnace-lined Gut as its huge jaws hinged open. When they slammed shut upon the helpless town, the part of it where Anna and her parents were cowering had buckled and her mother had lost her grip on Anna’s hand and tumbled through a gap that opened suddenly between two deckplates, down into the oily workings of the town’s massive caterpillar tracks. The tracks had been moving at full speed and had crushed Anna’s mother in an instant, but they could not pull the town free of Arkangel’s jaws, and it had been dragged backwards into the city’s Gut amid a cacophony of machinery and stressed metal. It was so loud that Anna had not even been able to hear own screams as Arkangel’s soldiers separated her from her father and dragged them off to join the other slaves.

Ever since, she had lived in Arkangel’s belly while it skated endlessly across the ice sheets on its huge runners. She had lost everything: even her name had been replaced with a number: K-420. She had become one of the countless thralls who serviced the dismantling machines and the huge engines. (“Thralls” was what they called their slaves in Arkangel. Anna supposed the people who lived on the city’s warm and comfortable upper tiers thought it sounded nicer.)

And now Arkangel had eaten yet another town, and Anna’s work gang had been detailed to sort through the mounds of salvage that had been thrown off it so that the giant saws and cutting torches and mechanical pincers could start ripping its upperworks apart.

It was in one of those mounds that Anna found the engines. There was a lot of old machinery there, probably the contents of some air-chandler’s store. Most of it was junk, and the two engine pods lay side by side among it, rusty and dusty and missing their propellers, so that anyone who hadn’t lived aboard an airship might not have known what they were at all. But Anna knew. She wiped the grime off a brass plaque with the cuff of her overalls, and there was the makers’ logo, the curly-tailed dragon she had liked so much when she was little.

It was confusing to have such a vivid memory of her childhood called up so suddenly and so clearly. Mostly Anna tried not to remember those times. It wasn’t because the memories were bad ones: it was because they were good. She had been happy in the sky with Ma and Pa, and she knew that if she thought about that time too often, it would make her so sad that she would die.

People died often in the thrall yards; from accidents, from illness, or just worn out by endless work. Thralls were allowed few comforts, and precious little food, especially in deep winter when prey was scarce. Anna’s father had been assigned to a different part of the Gut, but for the first few months he kept finding ways to visit Anna and slip a little extra food to her. Each time he looked thinner. At first he would tell her that they would find a way out, but she soon realized that he did not believe that, and before long he stopped bothering to say it. His eyes, which had been twinkly and full of fun and love for her when she lived in the sky, turned as dull as the windows of an empty house. One day he did not come at all, and after a week without seeing him Anna asked her overseer what had become of him and the overseer talked with an overseer from Pa’s work gang and then told her with a small shrug, “Dead.”

The overseer’s name was Verna Mould. She was a hard woman, but she was not unkind (it was she who had allowed Anna’s father to visit, and asked only a small part of the extra rations in return). Seeing Anna’s mouth start to tremble as the bad news sank in, she added helpfully, “He’s as dead as you’ll be, girly, if you waste your time in grieving. If you want to survive down here, you got to stop caring about anyone but yourself. You start fretting about others, or moping and mourning and thinking about old times, you’ll waste away and die like he did, or get careless and stand in the way of a salvage grab, or fall into a smelter. Forget all that stuff and you can thrive down here. You might end up being made an overseer yourself one day. That’s the best life a thrall can hope for aboard the Hammer.”

So Anna had tried to forget everything, or at least to bundle her memories up and stuff them away in some dark room deep inside herself. But now she was running the tips of her fingers over the cute little embossed dragons on a pair of Jeunet Carot engine pods, just as she had as a little girl, and it was as if a key had come to unlock that room and let the cold, clear sunlight of long ago shine in painfully on everything.

She wiped her eyes on the sleeve of her greasy overalls and tried to think straight. There were rewards for thralls who found valuable pieces of salvage. There would be extra rations of food, and Verna Mould would let Anna keep some of it for herself. Even so, she still hesitated for a moment before she let anyone know of her discovery. She felt that the aviator whose ship these engines came from must have been proud of them once and would think it a shame that they had ended up here, in the belly of Arkangel.

But she knew that if she didn’t claim the bonus, one of her comrades would, so she turned and shouted, “Here! Here! Salvage! Two old aero-engines, might still be good for parts…”