He was satisfied that Mr. Milburgh would not commit suicide, and the information was superfluous that Sam Stay had murdered Mrs. Rider. It was the knowledge that this vengeful lunatic knew where Odette Rider was staying which made Tarling sweat.
"He has gone to Cambours Restaurant to meet somebody, sir," said the sergeant.
The somebody was one of Milburgh's satellites at Lyne's Store. Tarling must see him without delay. The inspector had control of all the official arrangements connected with the case, and it would be necessary to consult him before he could place detectives to watch the nursing home in Cavendish Place.
He found a cab and drove to Cambours, which was in Soho, and was fortunate enough to discover Whiteside in the act of leaving.
"I didn't get much from that fellow," Whiteside began, when Tarling handed him the letter.
The Scotland Yard man read it through without comment and handed it back.
"Of course he hasn't committed suicide. It's the last thing in the world that men of the Milburgh type ever think about seriously. He is a cold-blooded villain. Imagine him sitting down to write calmly about his wife's murderer!"
"What do you think of the other matter--the threat against Odette?"
"There may be something in it," he said. "Certainly we cannot take risks. Has anything been heard of Stay?"
Tarling told the story of the stolen taxicab.
"We'll have him," said Whiteside confidently. "He'll have no pals, and without pals in the motor business it is practically impossible to get a car away."
He got into Tarling's cab, and a few minutes later they were at the nursing home.
The matron came to them, a sedate, motherly lady.
"I'm sorry to disturb you at this hour of the night," said Tarling, sensing her disapproval. "But information has come to me this evening which renders it necessary that Miss Rider should be guarded."
"Guarded?" said the matron in surprise. "I don't quite understand you, Mr. Tarling. I had come down to give you rather a blowing up about Miss Rider. You know she is absolutely unfit to go out. I thought I made that clear to you when you were here this morning?"
"Go out?" said the puzzled Tarling. "What do you mean? She is not going out."
It was the matron's turn to be surprised.