Sutton's lantern slipped out of his hand and crashed into the water, wavering under the thick, filthy stream for a moment or two, then going out.

"What was that?" Runcorn said hoarsely. "Water?"

"No." Sutton held Snoot more tightly.

"What?" Rathbone demanded.

"Fire," Sutton croaked.

"God Almighty!" Rathbone leaned against the wall. In the yellow glare his face was gray.

"Reckon as Mr. Sixsmith knows we're on to 'im," Orme observed. "Pity we din't get 'im. 'E's a real bad one."

"That hardly begins to describe him," Crow said bitterly. "We'll go back."

No one answered him; none of them wanted to argue the realities. They turned and started to retrace their steps until they were at the fork again.

"Other way?" Runcorn asked Sutton.

Sutton shook his head. "That's the way o' the fire. We need ter go back the way we come."

"Waters deeper," Crow pointed out.

"I know." Sutton started forward without adding anything. They went after him, each apparently lost in his own thoughts.

Monk tried hard not to let his mind go to Hester and Scuff. It would take from him his anger and the strength it gave him to go on through the icy, stinking water up to his knees and the filth that was in it. He knocked against the bodies of dead rats. Ahead of him Sutton was still carrying the little dog. Had he any idea at all where they were, or what was ahead of or behind them, except rockfalls and fire?

They turned more corners and passed a weir. The water thundered over the drop so violently they could not hear each other, even if they shouted.

Sutton waved to the left, pointing to another passage.

"That's…" Runcorn cupped his hands around his mouth and yelled, but his words were lost.

Orme looked at Monk.

Crow shrugged and followed after Sutton.

Monk and Rathbone had no better knowledge of the tunnels. All six of them and Snoot crossed over, gripping each other through the fast flowing stream, only just keeping their balance.

The tunnel curved around and started to go upwards. Then, just as Monk was thinking he could smell fresh air, it came to an abrupt end. There was water flowing from the left, a thin, steady spout out of the raw earth already carrying soil with it, and growing stronger even as they watched.

"It's going to burst through!" Rathbone said, his voice high, beyond his control. "We'll be drowned!" He swiveled around to look for escape. The tunnel behind him sloped downward, the way the water would flow.

Monk saw it and understood. There was no escape. Oddly now, with disaster so close, his fear was under control.

Snoot began to bark, writhing to get from Sutton's grasp.

" 'E can smell rabbits," Sutton said quietly. "We ain't got no other way. If we break this the stream'll come, but it isn't big. I reckon as we 'it wot they used to call the Lark, afore it went under. It in't very deep. We'll get proper wet and cold, but keep goin' an' we'll come out." And without waiting for approval he attacked the soil with his hands.

Monk looked at Rathbone, then at the others. Snoot was already digging just as fiercely as his master. Monk stepped forward and joined them, then so did the others.

The stream broke through in a rush, almost knocking them off their feet. Sutton fell against Runcorn, and Crow bent to help them back to their feet. The lanterns were all shattered, and they were plunged into obliterating darkness. There was no sense of direction except that of the icy water.

"C'mon!" Sutton shouted.

There was nothing to do for survival except to follow him into the stream. They crawled against the water, trying to breathe, to keep hold of anything, to move forward, upward, clinging, gasping, cold to the bone.

Monk had no idea how long it went on, how many times he thought his lungs would burst. Then suddenly there was light, real daylight, and air. He fell out after Sutton into the shingle bed and stumbled up the sides of the stone culvert. He turned immediately to see who was behind him. One by one the others dragged themselves out, filthy, drenched, and shuddering with cold. He swung around to thank Sutton, and saw with a wave of boundless relief that he had Snoot in his arms. "Is he all right?" he demanded.

Sutton nodded. "Thought 'e weren't," he said shakily. "But 'e's breathin'."

"Thank you, sir." Rathbone held out his hand to Sutton. "You have saved our lives. Now we must go and deal with Mr. Sixsmith. I suggest you get your dog warm." He fished in his pocket and brought out a gold sovereign. "Be so good as to give him a teaspoon of brandy with my compliments."

Monk felt the emotion well up inside him too intensely for him to speak. He met Sutton's eyes, looked again to make sure that Snoot was indeed breathing, and clasped Rathbone's arm very briefly. Then they followed Crow, who seemed to know which way to go.

The five of them were perishing with cold and smeared with clay and remnants of sewage when they reached the head of the tunnel again. They found Finger and almost twenty other navvies near the great machine.

Finger saw Monk. "We got another cave-in, bad one," he said grimly. "Blimey! Yer look like bloody 'ell!"

"Very well observed," Monk replied. "Too accurate to be accounted abusive language. Where is Sixsmith?"

"Down there." Finger pointed at the entrance.

Monk looked at it and a wave of nausea enveloped him. He could not go in that again. He simply physically could not. His legs were shaking, his stomach sick.

It was Runcorn who walked forward, his face set like stone. "I'll get that bastard up here," he said grimly. "Or I'll bring the whole bloody lot in on both of us."

"What! Runcorn!" Monk shouted after him. He swore violently. He could not let Runcorn go in there. He had no choice. He charged back into the semidarkness a pace behind Runcorn, still shouting at him.

Fifty yards in, the tunnel was still dimly lit from lanterns on the wall. A hundred yards and the glow came from ahead of them and Runcorn stopped abruptly.

Monk caught up with him. "Fire," he said, his voice catching. "I can feel the heat of it. Where's Sixsmith?"

Monk pressed forward again, more slowly now. He had covered another twenty yards around a curve when he saw the broad-chested figure ahead of him. It was unmistakably Sixsmith from the way he walked. He was coming towards them. He must have recognized Monk at that same moment. He stopped and stood with his arms loosely by his sides. If he was surprised to see Monk was not alone, there was nothing in his voice to betray it.

"You'd better let me past. There's fire behind me, and I'm the only one who can put it out! If I don't, it could come up into the streets and burn the whole of London."

"Did you mean to kill Toby Argyll?" Monk asked without moving.

"Eventually," Sixsmith replied. "But Mary taking him over with her was a piece of luck. I had intended to have him blamed for her death, but the way it worked out was better. Don't waste time, Monk. The fire'll break through soon. That whole tunnel behind me is ablaze. There's enough air in here to feed it."

"Why did you do it? For the Argyll Company?"

"Don't be so damn stupid! For revenge. Alan Argyll took my invention, the money, and far more than that, he took the praise for it! I don't give a damn if this whole thing blows up, Monk, but you do! You won't let the city burn, so get out of my way! I can put it out! Those fools up there don't know what to do."

Behind Monk, Runcorn was moving. Monk swung around to see what it was, and at that instant Runcorn threw the rock. It caught Sixsmith just as he raised his hand with the gun in it. He fell backwards as the shot exploded, and the bullet hit the rocks.

"Run!" Runcorn yelled, grabbing Monk by the waist and almost pulling him off his feet.