"I see." Her answer was simple. She was not a beautiful woman, her looks being rather more individual, but at this moment there was a true beauty in her face as she turned back to Rathbone. "We'll celebrate when we have it right," she said calmly. "I shall explain to Mama and Papa, and we can finish dinner quite pleasantly, and then go home. Please do what is necessary. It cannot wait. Whatever time it takes, however difficult it is, it must be accomplished before Argyll is charged and tried. They would hang him for James Havilland's death. Perhaps for Mary's as well, although I suppose it could have been Toby who was to blame for that. Do you suppose Toby did that for Sixsmith?"

Rathbone was thoughtful, but he did not take his eyes from her face. "Possibly, but he might not have realized all the implications. Sixsmith could have asked him to speak to her, try to persuade her that her father's death was suicide after all, and that she was only making it worse by continuing to probe it. Almost certainly he would try to persuade her that there was no danger in the tunnels."

"Was that what James Havilland was afraid of, uncharted underground rivers?" She turned to Monk.

"Yes, I think so. Toby seems to have spoken to toshers a lot, too, but that could have been to try to stop them from interfering with the work. That's what I thought to begin with. I don't think we'll ever know if he meant to kill Mary. Probably not. Not unless there was far more between him and Sixsmith than we know." He tried to visualize again what he had seen on the bridge. "I think it was an accident. She was frightened of him. Perhaps she thought Alan Argyll was behind her father's death and that Toby was going to kill her, too. She tried to get away from him, and whether she meant to or not, she took him with her." As he said it, he was not sure if that was what he really believed. Could Sixsmith deliberately have corrupted Toby Argyll? He remembered Alan Argyll's grief when he had heard of his brother's death. Grief, or guilt?

"We won't know, will we?" Margaret said sadly.

"Probably not," he admitted.

"And Mrs. Argyll?" she persisted. "She swore it was her husband who told her to write the letter."

"I know," Rathbone answered her. "There are a lot of things we still have to learn, and to prove. But we can't afford to wait. I'm sorry."

"I understand." She gave him a smile that was intimate and a little sad, but only for the moment missed, no more. She excused herself and left.

Rathbone looked at Monk. For the first time since Rathbone had realized he was in love with Hester, there was no envy in his eyes, only a deep happiness. He smiled at Monk.