"By hypothesis certainly. I may say that I have had some experience in criminal cases; accordingly I was very careful not to disturb anything, and up to this time I had only touched the man's wrist to assure myself that the pulse was gone." "Who was it that gave the alarm?" "I am told that one of the servants, Effingham, to be precise, knocked on the library door at about half past one o'clock, to announce the serving of luncheon. He then went away without waiting for an answer from Mr. Graeme; it seems that was his custom on the occasion of this particular summons. A half hour later, when Mr. Graeme failed to appear at the table, Miss Trevor told Effingham to go again and make sure that his master had heard the message. I understood that occasionally Graeme would not come to luncheon, especially if he happened to be more than usually busy; he might appear an hour or so later, and forage around for a glass of milk and a couple of biscuits." "His tardiness then excited no surprise?" "Apparently not. But Effingham went again to the library, and knocked two or three times without getting any response." "Must have been very alarming to Miss Graeme." "Oh, luckily Betty wasn't at home. Miss Trevor was alone in the house, and everything devolved upon her. Finally she decided to have the door broken down, but after she had given the order Effingham reminded her that it would not be necessary. A few months before Graeme had installed a complete system of modern locks throughout the house, and the butler had the master key in his possession." "That's an interesting point." "Yes--very. Well, Effingham went to the butler's pantry and got the key." "Oh, then it was not in his immediate possession after all?" "I believe he was in the habit of keeping it behind the clock in the pantry instead of with his regular bunch. Of course the idea was that if any of the ordinary keys were lost, or indeed the whole lot of them, he would still have the master key in reserve." "Do you suppose that anyone else--especially among the other servants--knew about the master-key and where it was kept?" "Effingham is quite sure that no one did know, but really it's impossible to say. You understand what darkies are--as curious as magpies and quite as lighthanded. If one of them had chanced to see Effingham hiding something behind the clock, he would be sure to investigate for himself at the first convenient opportunity." "While a clever thief, guessing that a master-key must be in existence, would go straight to such a prominent object as a clock for his first try. Curious, isn't it, how human nature prefers beaten trails, the old ruts, the obvious grooves in which to run. Take the ordinary small suburban house, with nobody home and everything supposed to be tightly locked up. It's a one-to-three shot, at least, that the front door key will be found neatly tucked away under the mat. But I shouldn't have interrupted."