She got the hatch down just in time, as an even bigger clot buried the construct completely. By the time that had been removed, the air inside was stale. A day had gone by since her escape from the patterner.

The black miasma, which had advanced and retreated a number of times, was now flowing steadily across the floor. It would be up to their knees within minutes.

'Better bring the prisoners on board,' she said to Merryl, who was anxiously watching the fumes. Tiaan popped the amplimet out and pocketed it, just in case. There was no room for trust; the whole world seemed to be against her.

The prisoners were brought in and taken below. Minis gazed sorrowfully at her, like a dog that had been kicked. Nish, who looked as though he hadn't slept in days, simply lay down, pillowed his head on his arms and went to sleep. Tirior showed no expression at all. She was the one to watch.

Everyone came aboard save the two who were mattocking away at the sticky tar on the right-hand side. When the black fog was at the level of their thighs, Tiaan called them in. Should a sudden surge overwhelm the construct now, it would be impossible to get out.

Merryl set guards on the Aachim and Nish. The remaining slaves went below, leaving just her and Merryl in the operator's compartment. It would be very cramped down there, with nine passengers. Tiaan reinserted the amplimet and took hold of the trumpet-shaped lever. The whine rose in pitch but the construct did not move.

'It's still stuck in the tar,' said Merryl. ' I don't think -'

'I'll try to work it free.'

He peered anxiously ahead. A billow of black mist was rolling towards them. Tiaan pulled down the hatch and fastened it. It became dark inside, except for the subtle glow from the plate in front of her. The front panel thinned to transparency. The outside was dimly lit by glowing globes that shone intermittently through the fog.

She wiggled the lever back and forth, ever so gently. The whine rose and fell. With a delicate shudder the construct pulled free and rose in the air until its base was at the level of the black fog. Tiaan edged it forwards.