It was ten o'clock in the morning, and Whiteside and Tarling were sitting on a sofa in their shirt-sleeves, sipping their coffee. Tarling was haggard and weary, in contrast to the dapper inspector of police. Though the latter had been aroused from his bed in the early hours of the morning, he at least had enjoyed a good night's sleep.

They sat in the room in which Mrs. Rider had been murdered, and the rusty brown stains on the floor where Tarling had found her were eloquent of the tragedy.

They sat sipping their coffee, neither man talking, and they maintained this silence for several minutes, each man following his own train of thought. Tarling for reasons of his own had not revealed his own adventure and he had told the other nothing of the mysterious individual (who he was, he pretty well guessed) whom he had chased through the grounds.

Presently Whiteside lit a cigarette and threw the match in the grate, and Tarling roused himself from his reverie with a jerk.

"What do you make of it?" he asked.

Whiteside shook his head.

"If there had been property taken, it would have had a simple explanation. But nothing has gone. Poor girl!"

Tarling nodded.

"Terrible!" he said. "The doctor had to drug her before he could get her to go."

"Where is she?" asked Whiteside

"I sent her on an ambulance to a nursing-home in London," said Tarling shortly. "This is awful, Whiteside."

"It's pretty bad," said the detective-inspector, scratching his chin. "The young lady could supply no information?"

"Nothing, absolutely nothing. She had gone up to see her mother and had left the door ajar, intending to return by the same way after she had interviewed Mrs. Rider. As a matter of fact, she was let out by the front door. Somebody was watching and apparently thought that she was coming out by the way she went in, waited for a time, and then as she did not reappear, followed her into the building."

"And that somebody was Milburgh?" said Whiteside.

Tarling made no reply. He had his own views and for the moment was not prepared to argue.

"It was obviously Milburgh," said Whiteside. "He comes to you in the night--we know that he is in Hertford. We know, too, that he tried to assassinate you because he thought the girl had betrayed him and you had unearthed his secret. He must have killed his wife, who probably knows much more about the murder than the daughter."

Tarling looked at his watch.

"Ling Chu should be here by now," he said.

"Oh, you sent for Ling Chu, did you?" said Whiteside in surprise. "I thought that you'd given up that idea."

"I 'phoned again a couple of hours ago," said Tarling.

"H'm!" said Whiteside. "Do you think that he knows anything about this?"

Tarling shook his head.

"I believe the story he told me. Of course, when I made the report to Scotland Yard I did not expect that you people would be as credulous as I am, but I know the man. He has never lied to me."

"Murder is a pretty serious business," said Whiteside. "If a man didn't lie to save his neck, he wouldn't lie at all."

There was the sound of a motor below, and Tarling walked to the window.

"Here is Ling Chu," he said, and a few minutes later the Chinaman came noiseles............