"I don' go there no more," Blackie said with a twist of his mouth. "I know which ones is safe an' which in't. But yer listen ter me, Sutton! Water, gas, fire, an' rats in't all there is ter watch fer! There's money in this, so there's men as'd commit murder. Keep out o' it, see? Go, an' take that lad there wi' the eyes out of 'ere. I dunno wot yer come fer, but there's nothin' 'ere fer you."

"I reckon not," Sutton agreed. Taking Hester by the arm, holding her hard, he turned and started back the way they had come. They had gone a hundred yards before Hester dared speak.

"Mary can't have come down here, surely?" she asked a little shakily.

"Mebbe, mebbe not, but they know about 'er," Sutton replied. "She must 'ave asked a lot o' questions-the right ones, by the sound o' it."

"But they wouldn't tell her anything," she protested. "What harm could she have done that they killed her?"

"I dunno," he admitted unhappily. "But if anyone killed 'er, it must'a bin Toby Argyll. Thing is, 'oo told 'im ter?"

"I need to know!" she insisted. "Otherwise, how do we prove that she didn't kill herself?"

"I 'ave ter know, too," he agreed. "Or 'ow do we stop 'em from goin' on faster and faster till they bring the 'ole bleedin' roof in an' mebbe bury an 'undred men alive? Or worse 'n that, set the gas alight an' start 'nother Great Fire o' London?"

She said nothing. She did not know the answer, but it troubled her. If Mary had been right, could she possibly have been the only one to see the danger? Surely her questions alone would have been sufficient to alarm other people. Was that what Alan Argyll had been concerned about, not the actual situation but the fears and suspicion Mary was stirring up? Was there ever cause to think it could have started a panic?

"They don't seem afraid," she said aloud. "They don't really think it'll happen, do they?"

Sutton looked at her. "Afraid o' wot?" he said gently. "Think about it too 'ard, an' yer'll be afraid o' the 'ole o' life. Bein' 'urt, bein' ungry, bein' cold, bein' alone. Or yer mean bein' drownded or buried alive? Don't think too far ahead. Just do terday."

"Is that what Argyll counts on? Poor Mary."

"Dunno," he confessed. "But it don't make sense like it is."

She did not argue, and they walked in companionable silence to the bus stop.

Monk was standing in the kitchen when he heard Hester come in at the front door. He spun around and strode into the hall. He immediately saw how she was dressed and that her face was pinched and weary. Her hair was straggling as if she had tied it in a knot rather than bothered dressing it at all, and her sleeves and trousers were wet.

"Where in hell have you been?" he said abruptly, alarm making his voice sharper than he had meant. He was very close to her, almost touching her. "What's happened?"

She did not even try to prevaricate. "I've been in the tunnels, with Sutton. I'm perfectly all right, but there's something terribly wrong there," she said, looking directly at him. "It isn't as easy as I thought. The engines are enormous, and they're shaking the ground. It's nothing to do with what James Havilland or Mary discovered. They all know it's dangerous; it's part of the job." Her eyes were searching his face now, looking for help, explanations to make sense of it. "They all know about the fact that there are streams underground, and wells, and that the clay slips. Hundreds of people live down there! But Mary was going from one person to another asking questions. What could she have been looking for, and why did it matter?"

Monk forced himself to be gentle as he accompanied Hester into the warmth of the kitchen. He was not in the least domestic by nature, but he had nonetheless cleaned out the stove and relit it. With Hester's absences in the clinic caring for the desperately ill and dying, he had been obliged to learn.

He took her coat from her and hung it up on the peg, where it could dry. She made no attempt to be evasive, which in itself alarmed him. She must be very badly frightened. He could see it in her eyes in the brightness of the kitchen gaslight. "Where did you learn all this?" he asked.

"The Thames Tunnel," she answered. "Not alone!" she added hastily. "I was perfectly safe." Involuntarily she shuddered, her body in a spasm of uncontrollable memory. She pushed a shaking hand through her hair. "William, there are people who live down there, all the time! Like… rats. They never come up to the wind or the light."

"I know. But it's probably no more a root of crime than the waterside slums or the docks, places like Jacob's Island." He put his arms around her and held her close. "You're not setting up any clinic for them!"

She laughed in spite of herself, and ended up coughing. "I hadn't even thought of it. But now that-"

"Hester!"

She smiled brightly at him.

He breathed out slowly, forcing himself to be calmer. Then he put more water in the kettle and slid it onto the hob. There was fresh bread and butter and cheese, and a slice of decent cake in the pantry.

"William…"

He stopped and faced her, waiting.

At last she spoke. "Mary went to all sorts of places and asked questions about rivers and clay, and how many people had been hurt, but she asked about engineers as well. And apparently she knew something about them-knew one sort from another. She took terrible risks. Either she didn't realize, or…" Her eyes suddenly filled with tears. She was so tired her skin was white, and in spite of his holding her, she had not stopped shivering.

"Do you think she was foolish enough to be unaware of the dangers?" he asked.

"No," she said in a soft, unhappy voice, but she did not pull away from him. "I think she cared about the truth so passionately that she preferred to take the risk rather than run away. I think she was afraid of a real disaster, worse than the Fleet."

"Because it's in a tunnel?"

"Fire," she told him. "Gas pipes go up into houses aboveground as well."

He understood. The possibilities were terrifying. "And they know?"

She nodded and moved back a step at last as the shivering eased. "It looks like it. She just couldn't prove it yet. Or maybe she could. Do you think that's why she was killed?"

"It could be," he said gently. "And it also might be why her father was killed, so don't imagine they would give a moment's thought as to whether or not they should kill you if they see you as a threat! So-"

"I know that! I have no intention of going back there again, I promise."

He looked at her closely, steadily, and saw the fear in her eyes. She would keep her word; he did not need to ask her for a promise. "Not only your life," he said, his voice softer. "The lives of others, too."

"I know. What are you going to do?"

"Make the tea," he said ruefully. "Then I'm going to consider who had the opportunity to kill James Havilland. As for Mary's death-we'll never prove that Toby meant to kill her, and since he died as well, the matter of justice has been rather well settled."

"Do you think she held on to him and took him with her on purpose?" she asked.

"Yes," he said. "I think she could do that."

"It isn't enough, though, is it?"

He could never lie to her. She could see right inside him, whether she meant to or not.

"No. It doesn't make sense that Alan Argyll would take a risk like that. It would ruin him. There's something else that we don't know. We haven't got all of it."

She put her arms around him again, holding him more tightly.

In the morning the situation seemed less clear-cut. If it had been Toby Argyll, young and ambitious, who was behind it all, then he was beyond anyone's reach now, and blackening his name would be seen as pointlessly cruel. Alan Argyll would do everything possible to prevent that, and Monk would earn for the River Police a bitter enemy. His proof would have to be absolute. No one would care about rescuing the reputation of James Havilland, and even less about Mary's. Naturally Farnham would see no purpose in it at all.