"Oh, no. I have told you that at 10.20 I went to the Controller's room, and after that I went out two or three times on one occasion or another. But each time I locked the door of the room." "Oh, you did? That is important. And you took all your keys with you, I presume?" "Yes, all. The keys on the bunch I took in my pocket, of course, and the room door key I also took. There are one or two rather important papers on my desk, you see, and anybody from the corridor might come in if the door were left unlocked." "The lock of the door would be a good deal easier to pick than that of the safe," Hewitt observed, after examining it. "But that would be of no great use with the safe locked. Shortly, then, the facts are these. You locked the code safely away at 10.20, you left the room two or three times, but each time the door, as well as the safe, was locked, and the keys in your pocket; and then, at 12.20, or two hours exactly after the code had been put safely away, you opened the safe again in presence of the Controller's secretary, and the code had vanished. That is the whole matter in brief, I take it?" "Precisely." Mr. Telfer was pallid and bewildered. "It seems a total impossibility," he said; "a total, absolute, physical impossibility; but there it is." "But as no such thing as a physical impossibility ever happens," Hewitt replied calmly, "we must look further. Now, are there any other ways into this room than by that door into the corridor? I see another door here. What is that?" "That door has been locked for ages. The room on the other side is one like this, with a door in the corridor; it is used chiefly to store old documents of no great importance, and I believe that whole stacks of them, in bundles, are piled against the other side of that same door. We will send for the key and see, if you like." The key was sent for, and the door from the corridor opened. As Telfer had led us to expect, the place was full of old papers in bundles and parcels, thick with ancient dust, and these things were piled high against the door next his room, and plainly had not been disturbed for months, or even years. "There remains the skylight," said Hewitt, "for I perceive, Mr. Telfer, that your room is lighted from above, and has no window; while the grate is a register. There seems to be no opening in that skylight but the revolving ventilator. Am I right?" "Quite so. There is no getting in by the skylight without breaking it, and, as you see, it has not been broken. Certainly there are men on the roof repairing the leads, but it is plain enough that nobody has come that way. The thing is wholly inexplicable." "At present, yes," Hewitt said, musingly. He stood for a few moments in deep thought. "Plummer is longer away than I expected," he said presently. "By the way, what was the external appearance of the missing code?"