2 might very easily lead to the dead end of Milburgh's innocence.
He felt a sense of relief, however, that the authorities had acted so promptly in impounding Lyne's books.

An examination into these might lead to the discovery of the murderer, and at any rate would dispel the cloud of suspicion which still surrounded Odette Rider.
He had gone to Dashwood and Solomon to make himself personally acquainted with that string in the tangled skein which he was determined to unravel; and now, with his mind at rest upon that subject, he was returning to settle matters with Ling Chu, that Chinese assistant of his who was now as deeply under suspicion as any suspect in the case.
He had spoken no more than the truth when he had told Inspector Whiteside that he knew the way to deal with Ling Chu.

A Chinese criminal--and he was loath to believe that Ling Chu, that faithful servant, came under that description--is not to be handled in the Occidental manner; and he, who had been known throughout Southern China as the "Hunter of Men" had a reputation for extracting truth by methods which no code of laws would sanction.
He walked into his Bond Street flat, shut the door behind him and locked it, putting the key in his pocket.

He knew Ling Chu would be in, because he had given him instructions that morning to await his return.
The Chinaman came into the hall to take his coat and hat, and followed Tarling into the sitting-room.
"Close the door, Ling Chu," said Tarling in Chinese.

"I have something to say to you." The last words were spoken in English, and the Chinaman looked at him quickly.