"There is no witness so sure as the camera," remarked Malcolm Sage as he gazed from one to the other of two photographs before him, one representing him holding an automatic pistol to his own head, and the other in which Sir James was posing as a murderer. "It is strange that it should be so neglected at Scotland Yard," he added. Silent and absorbed when engaged upon a problem, Malcolm Sage resented speech as a sick man resents arrowroot. At other times he seemed to find pleasure in lengthy monologues, invariably of a professional nature. "But we use it a lot, Mr. Sage," protested Inspector Wensdale. "For recording the features of criminals," was the retort. "No, Wensdale, you are obsessed by the finger-print heresy, quite regardless of the fact that none but an amateur ever leaves such a thing behind him, and the amateur is never difficult to trace." He paused for a moment; but the inspector made no comment. "The two greatest factors in the suppression of crime," continued Malcolm Sage, "are photography and finger-prints. Both are in use at Scotland Yard; but each in place of the other. Finger-prints are regarded as clues, and photography is a means of identification, whereas finger-prints are of little use except to identify past offenders, and photography is the greatest aid to the actual tracing of the criminal." Malcolm Sage never failed to emphasise the importance of photography in the detection of crime. He probably used it more than all other investigators put together. He contended that a photographic print established for all time what the eye could only dimly register for the moment, with the consequent danger of forgetfulness. As the links in a chain multiplied, it was frequently necessary to refer to the scene of a crime, or tragedy, and then probably some important point would crop up, which the eye had not considered of sufficient importance to dwell upon. By then, in the case of a murder, the body would have been removed, and everything about it either re-ordered or obliterated. Malcolm Sage proceeded to stuff his pipe with tobacco which he drew from the left-hand pocket of his jacket. He had discovered that a rubber-lined pocket was the best and safest pouch. He picked up a third photograph and laid it beside the others. It was a print of Mr. Challoner's head, showing, marked in ink, the course of the bullet towards the left of the frontal bone. "A man shooting himself," began Malcolm Sage, "places the pistol in a position so that the muzzle is directed towards the back of the head. On the other hand, anyone approaching his victim from behind would have a tendency to direct the muzzle towards the front of the head. That is why I got Dawkins to take a photograph of me holding the pistol to my head and of you holding it from behind. These photographs will constitute the principal evidence at the trial." Sir James nodded. He was too interested to interrupt.