“The rest of us should sleep while we can,” Healhand suggested. “As soon as Arbor returns we will teach you how to behave like a slave.” Her smile was crooked and there was pain in her eyes.

“You must keep your eyes on the floor all the time. Remember that, Ruth. It is very important. You are nobody. You are nothing. “

Healhand's words echoed in Ruth's cars as she scrambled up the embankment wall above the dam and began to crawl along it. ‘You are nothing.’ If she were to slip now it wouldn't matter. She could catch hold of the bars that held back flotsam from the conduit into the Ark. It was once she reached the top of the dam that she would be in danger.

She crawled carefully along, the rough concrete painful against her bare knees. Here it was now, on her right. In the strong morning sun the water looked like a piece of synthetic drawn tight and smooth. Dark. Deep. And very fast.

She began the slow journey across the dam. She must not look down to the left. Swift had told her that. He had told her twice. Down there was a sheer drop to the rocks at the bottom, hidden from her by the spray that hung continuously in the air. The water poured through the sluice gates in a curve as smooth and hard looking as steel. Down it poured.

She forced her eyes away. You must not look. She swallowed nausea and crawled forward. The noise of the falling water battered at her cars until her head spun and she felt dazed and stupid. Its force shook the solid concrete of the dam. What would it be like to be in that water?

No, don't think about it. Go on. Not far now. She stared ahead to where the concrete foundation of the City met the embankment. Across there the containing wall forked. One part joined the dam itself, the other joined the foundations. In the small triangle of shadow within the fork lay the secret entrance to the City. Tomi's way.

Come on. The path is a metre wide and no more than ten metres long. It's nothing. She inched forward, her knees scraping the concrete. Halfway now. Three quarters. She slid feet first into shadow and felt ground securely beneath her bare soles.

There should be a door and a latch. There. Her fingers closed around it. She lifted the latch and pulled. The door swung open easily. Beyond was total darkness and the familiar smell of recycled air. She took one quick look up at the sunny sky, ducked her head and went down into darkness.