"I suspect that for some reason or other he returned to the laboratory; that accounts for the rough marks upon the door-fastenings as if someone had first torn them off and then sought to replace them. After his second visit the murderer evidently stayed too long, and was afraid of being seen leaving the laboratory. He therefore remained until the following night, eating the professor's meals. Incidentally he knew all about his habits." "Well, I'm blowed if he isn't a cool un!" gasped the inspector. Malcolm Sage rose with the air of one who has concluded the business on hand. "Can I run you back to town, Carfon?" he asked, as he walked towards the door. "No, thank you," said the inspector. "I must go over to Strinton and see Brewitt. He's following up a clue he's got. Some tramp who was seen hanging about here for a couple of days just before the murder," he added. "Unless he is tall and powerful, left-handed, with something more than a layman's knowledge of surgery, you had better not trouble about him," said Malcolm Sage quietly. "You might also note that the murderer belongs to the upper, or middle class, has an iron nerve, and is strongly humanitarian." For a moment Inspector Carfon stared at Malcolm Sage with lengthened jaw. Then suddenly he laughed, a laugh of obvious relief. "At first I thought you were serious, Mr. Sage," he said, "till I saw what you were up to. It's just like the story-book detectives," and he laughed again, this time more convincingly. Malcolm Sage shrugged his shoulders. "Let me have a description of the man when you get him," he said, "and some of the tobacco he smokes. Try him with marmalade, Carfon, and plenty of it. By the way, you make a great mistake in not reading _The Present Century_," he added. "It can be curiously instructive," and without another word he crossed the hall and, a moment later, entered his car. "Swank!" murmured Inspector Carfon angrily, as he watched Tims swing the car down the drive at a dangerous rate of speed, "pure, unadulterated, brain-rotting swank," and he in turn passed down the drive, determined to let Malcolm Sage see what he could do "on his own." II Three weeks passed and there was no development in the McMurray Mystery. Malcolm Sage had heard nothing from Inspector Carfon, who was busily engaged in an endeavour to trace the tramp seen in the neighbourhood of "The Hollows" on the day previous to the murder. Sir John Dene had called several times upon Malcolm Sage, whom he had come to regard as infallible, only to be told that there was no news. He made no comment; but it was obvious that he was greatly disappointed. Interest began to wane, the newspapers devoted themselves to other "stunts," and the McMurray Mystery seemed fated to swell the list of unfathomed crimes with which, from time to time, the Press likes to twit Scotland Yard.