Suddenly he stooped, and Bobby got on his knees beside him. The cylinder of light held in its centre one mark, clear and distinct in the trampled grass, and with a warm gratitude, a swift apprehension, Bobby thought of Katherine. For the mark in the grass had been made by the heel of a woman's shoe. "Not the foreigner then," Robinson mused, "not yourself, Blackburn, but a woman, a devoted woman. That's something to get after." "And if she lies, the impression of the heel will give her away," the coroner suggested. Robinson grinned. "You'd make a rotten detective, Coroner. Women's heels are cut to a pattern. There are thousands of shoes whose heels would fit this impression. We need the sole for identification, and that she hasn't left us. But she's done one favour. She's advertised herself as a woman, and there are just three women in the house. One of those committed this serious offence, and the inference is obvious." Before Bobby could protest, the doctor broke in with his throaty rumble: "One of those, or the woman who cried about the house." Bobby started. The memory of that eerie grief was still uncomfortable in his brain. Could there have been actually a woman at the stagnant lake that afternoon and close to the house to-night--some mysterious friend who assumed grave risks in his service? He recognized Robinson's logic. Unless there were something in that far-fetched theory, Katherine faced a situation nearly as serious as his own. Robinson straightened. At the same moment the scraping of a window reached them. Bobby glanced at the newer wing. Katherine leaned from her window. The coincidence disturbed him. In Robinson's mind, he knew, her anxiety would assume a colour of guilt. Her voice, moreover, was too uncertain, too full of misgivings: "What is going on down there? There have been no--no more tragedies?" "Would you mind joining us for a moment?" Robinson asked. She drew back. The curtain fell over her lighted window. The darkness of the court was disturbed again only by the limited radiance of the flashlight. She came hurriedly from the front door. "I saw you gathered here. I heard you talking. I wondered." "You knew there were footprints in this court," Robinson said harshly, "that Howells connected them with the murderer of your uncle." "Yes," she answered simply. "Why then," he asked, "did you attempt to obliterate them?" She laughed. "What do you mean? I didn't. I haven't been out of the house since just after luncheon." "Can you prove that?" "It needs no proof. I tell you so." The flashlight exposed the ugly confidence of Robinson's smile. "I am sorry to suggest the need of corroboration." "You doubt my word?" she flashed. "A woman," he answered, "has obliterated valuable testimony, I shall make it my business to punish her." She laughed again. Without another word she turned and reentered the house. Robinson's oath was audible to the others.