Muller was quite satisfied with the result of his visit to the accused. He hurried to the nearest cab stand and entered one of the carriages waiting there. He gave the driver Mrs. Klingmayer's address. It was about two o'clock in the afternoon now and Muller had had nothing to eat yet. But he was quite unaware of the fact as his mind was so busy that no mere physical sensation could divert his attention for a moment. Muller never seemed to need sleep or food when he was on the trail, particularly not in the fascinating first stages of the case when it was his imagination alone, catching at trifles unnoticed by others, combining them in masterly fashion to an ordered whole, that first led the seekers to the truth. Now he went over once more all the little apparently trivial incidents that had caused him first to watch the Thorne household and then had drawn his attention, and his suspicion, to Adele Bernauer. It was the broken willow twig that had first drawn his attention to the old garden next the Thorne property.

This twig, this garden, and perhaps some one who could reach his home again, unseen and unendangered through this garden - might not this have something to do with the murder?

The breaking of the twig was already explained. It was Johann Knoll who had stepped on it. But he had not climbed the wall at all, had only crept along it looking for a night's shelter. And there was no connection between Knoll and the people who lived in the Thorne house. Muller had not the slightest doubt that the tramp had told the entire truth that day and the day preceding.

Then the detective's mind went back to the happenings of Tuesday morning. The little twig had first drawn his attention to the Thorne estate and the people who lived there. He had seen the departure of the young couple and had passed the house again that afternoon and the following day, drawn to it as if by a magnet.

He had not been able then to explain what it was that attracted him; there had been nothing definite in his mind as he strolled past the old mansion. But his repeated appearance had been noticed by some one - by one person only - the housekeeper. Why should she have noticed it? Had she any reason for believing that she might be watched? People with an uneasy conscience are very apt to connect even perfectly natural trivial circumstances with their own doings. Adele Bernauer had evidently connected Muller's repeated passing with something that concerned herself even before the detective had thought of her at all.

Muller had not noticed her until he had seen her peculiar conduct that very morning. When he heard Franz's words and saw how disturbed the woman was, he asked himself: "Why did this woman want to be shown the spot of the murder? Didn't she know that place, living so near it, as well as any of the many who stood there staring in morbid curiosity? Did she ask to have it shown her that the others might believe she had nothing whatever to do with the occurrences that had happened there? Or was she drawn thither by that queer attraction that brings the criminal back to the scene of his crime?"The sudden vision of Mrs. Bernauer's head at the garden gate, and its equally sudden disappearance had attracted Muller's attention and his thoughts to the woman. What he had been able to learn about her had increased his suspicions and her involuntary exclamation when she met him face to face in the house had proved beyond a doubt that there was something on her mind. His open accusation, her demeanour, and finally her swoon, were all links in the chain of evidence that this woman knew something about the murder in the quiet lane.