"The doctor left, and I determined to give the man another chance with pen and paper. I felt pretty certain that if he were allowed to scribble and sketch as he pleased, sooner or later he would do something that would give me some sort of a hint. I left him entirely alone and let him do as he pleased, but I watched. "After all the futile scribble which you have seen, he began to sketch, first a man's head, then a chair--just what he might happen to see in the room. Presently he took to the piece of paper you have before you. He observed that clock and began to sketch it, then went on to other things, such as you see, scribbling idly over most of them when finished. When he had made the last of the sketches he made a hasty scrawl of his pen over it and broke down. It had brought his terror to his mind again somehow. "I seized the paper and examined it closely. Now just see. Ignore the clock, which was merely a sketch of a thing before him, and look at the three things following. What are they? A horse-shoe, a captive balloon, and a Highlander. Now, can't you think of something those three things in that order suggest?" I could think of nothing whatever, and I confessed as much. "Think, now. Tottenham Court Road!" I started. "Of course," I said. "That never struck me. There's the Horse-shoe Hotel, with the sign outside, there's the large toy and fancy shop half-way up, where they have a captive balloon moored to the roof as an advertisement, and there's the tobacco and snuff shop on the left, toward the other end, where they have a life-size wooden Highlander at the door--an uncommon thing, indeed, nowadays." "You are right. The curious conjunction struck me at once. There they are, all three, and just in the order in which one meets them going up from Oxford Street. Also, as if to confirm the conjecture, note the _dotted_ horse-shoe. Don't you remember that at night the Horse-shoe Hotel sign is illuminated by two rows of gas lights? "Now here was my clue at last. Plainly, this man, in his mechanical sketching, was following a regular train of thought, and unconsciously illustrating it as he went along. Many people in perfect health and mental soundness do the same thing if a pen and a piece of waste paper be near. The man's train of thought led him, in memory, up Tottenham Court Road, and further, to where some disagreeable recollection upset him. It was my business to trace this train of thought. Do you remember the feat of Dupin in Poe's story, 'The Murders in the Rue Morgue'--how he walks by his friend's side in silence for some distance, and then suddenly breaks out with a divination of his thoughts, having silently traced them from a fruiterer with a basket, through paving-stones, Epicurus, Dr. Nichols, the constellation Orion, and a Latin poem, to a cobbler lately turned actor?