Tarling, his hands thrust into his pockets, his chin dropped, his shoulders bent, slowly walked the broad pavement of the Edgware Road on his way from the girl's hotel to his flat. He dismissed with good reason the not unimportant fact that he himself was suspect. He, a comparatively unknown detective from Shanghai was by reason of his relationship to Thornton Lyne, and even more so because his own revolver had been found on the scene of the tragedy, the object of some suspicion on the part of the higher authorities who certainly would not pooh-pooh the suggestion that he was innocent of any association with the crime because he happened to be engaged in the case.

He knew that the whole complex machinery of Scotland Yard was working, and working at top speed, to implicate him in the tragedy. Silent and invisible though that work may be, it would nevertheless be sure. He smiled a little, and shrugged himself from the category of the suspected.

First and most important of the suspects was Odette Rider. That Thornton Lyne had loved her, he did not for one moment imagine. Thornton Lyne was not the kind of man who loved. Rather had he desired, and very few women had thwarted him. Odette Rider was an exception. Tarling only knew of the scene which had occurred between Lyne and the girl on the day he had been called in, but there must have been many other painful interviews, painful for the girl, humiliating for the dead millionaire.

Anyway, he thought thankfully, it would not be Odette. He had got into the habit of thinking of her as "Odette," a discovery which had amused him. He could rule her out, because obviously she could not be in two places at once. When Thornton Lyne was discovered in Hyde Park, with Odette Rider's night-dress round about his wound, the girl herself was lying in a cottage hospital at Ashford fifty miles away.

But what of Milburgh, that suave and oily man? Tarling recalled the fact that he had been sent for by his dead relative to inquire into Milburgh's mode of living and that Milburgh was under suspicion of having robbed the firm. Suppose Milburgh had committed the crime? Suppose, to hide his defalcations, he had shot his employer dead? There was a flaw in this reasoning because the death of Thornton Lyne would be more likely to precipitate the discovery of the manager's embezzlements--there would be an examination of accounts and everything would come out. Milburgh himself was not unmindful of this argument in his favour, as was to be revealed.

As against this, Tarling thought, it was notorious that criminals did foolish things. They took little or no account of the immediate consequences of their act, and a man like Milburgh, in his desperation, might in his very frenzy overlook the possibility of his crime coming to light through the very deed he had committed to cover himself up.

He had reached the bottom of Edgware Road and was turning the corner of the street, looking across to the Marble Arch, when he heard a voice hail him and turning, saw a cab breaking violently to the edge of the pavement.

It was Inspector Whiteside who jumped out.

"I was just coming to see you," he said. "I thought your interview with the young lady would be longer. Just wait a moment, till I've paid the cabman--by-the-way, I saw your Chink servant and gather you sent him to the Yard on a spoof errand."

When he returned, he met Tarling's eye and grinned sympathetically.

"I know what's in your mind," he said frankly, "but really the Chief thinks it no more than an extraordinary coincidence. I suppose you made inquiries about your revolver?"

Tarling nodded.

"And can you discover how it came to be in the possession of----" he paused, "the murderer of Thornton Lyne?"

"I have a theory, half-formed, it is true, but still a theory," said Taxiing. "In fact, it's hardly so much a theory as an hypothesis."

Whiteside grinned again.

"This hair-splitting in the matter of logical terms never did mean much in my young life," he said, "but I take it you have a hunch."

Without any more to-do, Tarling told the other of the discovery he had made in Ling Chu's box, the press cuttings, descriptive of the late Mr. Lyne's conduct in Shanghai and its tragic sequel.

Whiteside listened in silence.

"There may be something on that side," he said at last when Tarling had finished. "I've heard about your Ling Chu. He's a pretty good policeman, isn't he?"

"The best in China," said Tarling promptly, "but I'm not going to pretend that I understand his mind. These are the facts. The revolver, or rather the pistol, was in my cupboard and the only person who could get at it was Ling Chu. There is the second and more important fact imputing motive, that Ling Chu had every reason to hate Thornton Lyne, the man who had indirectly been responsible for his sister's death. I have been thinking the matter over and I now recall that Ling Chu was unusually silent after he had seen Lyne. He has admitted to me that he has been to Lyne's Store and in fact has been pursuing inquiries there. We happened to be discussing the possibility of Miss Rider committing the murder and Ling Chu told me that Miss Rider could not drive a motor-car and when I questioned him as to how he knew this, he told me that he had made several inquiries at the Store. This I knew nothing about.

"Here is another curious fact," Tarling went on. "I have always been under the impression that Ling Chu did not speak English, except a............