The flames stopped. She tried to move forwards but that did not work either. Blisters were rising on the back of her hand. 'Move!' she screamed. The walker gave only a spastic twitch. Its front feet were stuck in tar which had softened in the heat.

Hot tar ribboned onto her shoulders. She bent the four legs as far as they would go, then straightened them all at the same time. Three legs pulled free, the other did not, and the machine began to topple. Tiaan threw her weight the other way and managed to save it, though it left her directly in front of the cracks. The next blast would burn her to a crisp. She could hear it coming, a breathy roar.

Flexing the legs again, she gave a mighty heave. The stuck leg pulled free and the walker shot forwards and up as the flames roared by. Tiaan felt the heat on her backside.

Further on, she went down into a hollow where heavy black fumes had pooled on the floor. As the walker crabbed through it lifted inky tendrils as high as her head. Eyes stinging, she lurched down the corridor, having no idea where she was going. Since the explosion, Tiaan could not remember Merryl's directions, and most of the wall lamps had gone out. She just kept moving because she could not remain where she was.

Creeping along, breathing through her sleeve, she thought she heard human voices coming from one of the branching tunnels ahead. 'Hello!' she yelled.

No answer. She moved to the intersection. Definitely voices, from the middle tunnel. She crept up through the gloom, turned a corner into a wider tunnel lit by a single lantern on a pole, and stopped.

Half a dozen people had their backs to her, staring at something that she could not make out. They looked like the human slaves the lynnx had kept here. The walker's legs clacked and they turned, squinting into the dark. She moved forwards and, with wild cries, they broke and ran. What was the matter? Tiaan realised, belatedly, that she must have made a terrifying sight, half human and half machine, and coated with droppings of tar.