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 ?" Whiteside nodded.
"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.