There was no time for it. Life was regimented for war and everyone had their place in it. The work was tedious, the hours long, but crime was unheard of. No one was afraid to walk the streets at night.

To her left, another path tracked the snow under the aqueduct, then across the gash of the faultline before winding up the mountain to the tar mine. On rare hot days up there, tar oozed out of the shattered rocks and could be scraped into buckets. Mostly, though, the miners hacked solid tar from the drives or followed erratic seams of brittle pitch though the mountain. It was the worst job in the world, and few survived to old age, but someone had to do it. The furnaces of the manufactory must be fed. Its clankers were vital to the war. And the war was being lost.

Controllers were just as critical. Tiaan could imagine how the soldiers must have felt, attacked by ravening lyrinx and realising they had no protection because their clankers had stalled. She could not bear to think that it might have been her fault.

She hurried along the path to the lower mine, where the hedron crystals were found. It was twenty minutes' walk down a steep decline and Tiaan had plenty of time to fret, though she was no closer to a solution when she reached the main adit.

'Mornin', Tiaan!' Lex, the day guard, nodded at her from his cavern like a statue in a temple. His ill-fitting false teeth sat on the counter, as usual. Sometimes the miners hid them, sparking a frantic search and emotional outbursts.

'Morning, Lex. Where's Joe today, do you know?'

'Down on fif' level,' Lex mumbled. Without his teeth it was hard to make out what he was saying. 'Take six' tunnel on right an' follow to end.'