She kept silent and followed him patiently. At last-her feet sore and her boots and skirt splattered-she reached the point below which the men were actually working by flares at the face of the tunnel. The earth was excavated deeper than she had expected. She was close to the edge of the drop, and a feeling of vertigo overcame her for a moment as she stared down almost a hundred feet to the brickworks at the bottom of the abyss. She could quite clearly see the floor of what would be the new sewer, and the arching brick sides already laid and cemented. There was scaffolding over it holding the walls apart all the way up. Here and there other pipes crossed it. Fifty yards away, well on the other side, a steam engine hissed and thumped, driving the chains that held heavy buckets and scoops to draw up and empty the rubble and broken brick.

She turned and met Sutton's eyes. He pointed down to where she could see men below, foreshortened to funny little movements of hands and shoulders. They walked, pushing barrows. Others swung pikes or heaved on shovels of soil and rock.

"Look." Sutton directed her eyes towards the walls on the far side. The earth itself was held firm by planks of heavy wood, supported by crossbeams every few yards. Then she followed Sutton's gaze and saw the water seeping through-just a dribble here and there, or a bulge in the wood where the boards had been strained and were coming away.

On the bank opposite, stokers were keeping the great steam engine going. She could hear the wheeze and thump of its pistons and smell the steam, the oil.

She was aware of Sutton watching her. She tried to imagine what it would be like to work down in that cleft in the earth, seeing nothing but a slit of sky above you and knowing you couldn't get out.

"Where's the way up?" she asked almost involuntarily.

" 'Alf a mile away," he answered quietly. "All right ter walk ter, if yer in no 'urry. Nasty if yer need ter move quickish-like if 'em sides spring a leak."

"A leak? You mean a stream ... or something? You don't mean just rain?" The picture of that bulging wall giving way filled her mind-a jet of water gushing out, not just dribbling as it was now. Would it fill the bottom? Enough to drown them? Of course it would! Who could swim in a crevasse like that, with freezing water coming down on top of you?