“Well,” said the chief, “your argument is clever. We must admit that, if Gyde is the murderer, then Gyde has committed more faults in the business than it is at all probable he would commit. If Gyde is not the murderer, then, some other man is; if that is so, I am bound to admit that this other man has not only successfully fouled his traces but has cast, in some extraordinary manner, the onus of the affair upon Gyde. The proof of that is,” he continued, with a short laugh, “he has made us issue a warrant for Gyde’s arrest. Have you anything more to say, Freyberger? What you have said already has been to the point.” “Only this, sir. Dr Murrell is preparing the retina of the valet, Leloir. He intends photographing it by Mendel’s process. He may, or may not, succeed; the thing fails as a rule, or only gives the faintest blur of a picture. But it seems that the rods and cones of the retina take a far more powerful impression in a case like this, if the subject has caught his last glimpse of earthly things by the electric light. It is just possible that the retina of Leloir may give us a picture of what he saw before he died.” “The only two successful cases of the kind I have heard of,” said the chief, “occurred in Germany.” “That is true, sir,” replied Freyberger. “The case of Ludwig Baumer, recounted by Casper; and the case of the courtesan, Gretchen Dreschfeld, which Addeler, the professor of forensic medicine at Bonn, made such a success of.” “When did Dr Murrell say his results would be known?” asked the chief. “He did not say, sir; but, with your permission, I will call upon him now and see what hopes he can give us of a successful photograph.” “Do so,” said the chief. And Freyberger departed. ------------------------------------------------------------------------ CHAPTER XVII DR GUSTAVUS MURRELL lived in Sackville Street, Piccadilly. He was a man of private means, and he possessed a medical practice that brought him in about a thousand a year. One of those pleasant practices, where the lowest fee for looking at a tongue is a guinea, and for an operation fifty. He was a tall, well-groomed, handsome man of forty-five or so, with a jovial blue eye and a hearty manner. You never would have imagined that one of the chief hobbies of this healthy and happy-looking individual was grubbing in the cesspit of crime. Yet it was. Only one of his hobbies, for he had several, photography amongst the rest. Though a dilettante of criminal acts and possessed of a profound penetrative power, as far as human motives were concerned, Dr Murrell was no amateur detective. He studied criminals just as a botanist studies fungi; they interested him, and he felt a sort of sympathy for them, that sympathy which we all feel, more or less, for the things that interest us.