Pugh had left his puzzle box behind him. We had done all we could, together, to solve the puzzle. He had left it behind to see what I could do with it alone. So much had it engrossed my attention that I had even brought it into my bedroom, in order that I might, before retiring to rest, make a final attempt at the solution of the mystery. _Now_ what possessed the thing? As I stood, and looked, and listened, one thing began to be clear to me, that some sort of machinery had been set in motion inside the box. How it had been set in motion was another matter. But the box had been subjected to so much handling, to such pressing and such hammering, that it was not strange if, after all, Pugh or I had unconsciously hit upon the spring which set the whole thing going. Possibly the mechanism had got so rusty that it had refused to act at once. It had hung fire, and only after some hours had something or other set the imprisoned motive power free. But what about the screeching? Could there be some living creature concealed within the box? Was I listening to the cries of some small animal in agony? Momentary reflection suggested that the explanation of the one thing was the explanation of the other. Rust!--there was the mystery. The same rust which had prevented the mechanism from acting at once was causing the screeching now. The uncanny sounds were caused by nothing more nor less than the want of a drop or two of oil. Such an explanation would not have satisfied Pugh, it satisfied me. Picking up the box, I placed it to my ear. "I wonder how long this little performance is going to continue. And what is going to happen when it is good enough to cease? I hope"--an uncomfortable thought occurred to me--"I hope Pugh hasn't picked up some pleasant little novelty in the way of an infernal machine. It would be a first-rate joke if he and I had been endeavoring to solve the puzzle of how to set it going." I don't mind owning that as this reflection crossed my mind I replaced Pugh's puzzle on the dressing-table. The idea did not commend itself to me at all. The box evidently contained some curious mechanism. It might be more curious than comfortable. Possibly some agreeable little device in clockwork. The tick, tick, tick suggested clockwork which had been planned to go a certain time, and then--then, for all I knew, ignite an explosive, and--blow up. It would be a charming solution to the puzzle if it were to explode while I stood there, in my nightshirt, looking on. It is true that the box weighed very little. Probably, as I have said, the whole affair would not have turned the scale at a couple of ounces. But then its very lightness might have been part of the ingenious inventor's little game. There are explosives with which one can work a very satisfactory amount of damage with considerably less than a couple of ounces.