“I shall wish to ask you some questions in a few minutes, Mr. Paredes,” the district attorney said.

“At your service, I’m sure,” Paredes drawled.

He watched them until they had entered the court and closed the door.  The chill dampness of the court infected Bobby as it had always done.  It was a proper setting for his accusation and arrest.  For Robinson, he knew, wouldn’t wait as Howells had done to solve the mystery of the locked doors.

Robinson, while the others grouped themselves about him, took a flashlight from his pocket and pressed the control.  The brilliant cylinder of light illuminated the grass, making it seem unnaturally green.  Bobby braced himself for the inevitable denouement.  Then, while Robinson exclaimed angrily, his eyes widened, his heart beat rapidly with a vast and wondering relief.  For the marks he remembered so clearly had been obliterated with painstaking thoroughness, and at first the slate seemed perfectly clean.  He was sure his unknown friend had avoided leaving any trace of his own.  Each step in the grass had been carefully scraped out.  In the confusion of the path there was nothing to be learned.

The genuine surprise of Bobby’s exclamation turned Robinson to him with a look of doubt.

“You acknowledge these footmarks were here, Mr. Blackburn?”

“Certainly,” Bobby answered.  “I saw them myself just before dark.  I knew Howells ridiculously connected them with the murderer.”

“You made a good job of it when you trampled, them out,” Robinson hazarded.

But it was clear Bobby’s amazement had not been lost on him.

“Or,” he went on, “this foreigner who advertises himself as your friend!  He was in the court tonight.  We know that.”

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.”