I turned it over and over and cudgelled my brains; and then I had a brilliant idea.  Was it a reed pen of which the point had been broken off?  I knew that reed pens were still in use by draughtsmen of decorative leanings with an affection for the “fat line.”  Could any of our friends be draughtsmen?  This seemed the most probable solution of the difficulty, and the more I thought about it the more likely it seemed.  Draughtsmen usually sign their work intelligibly, and even when they use a device instead of a signature their identity is easily traceable.  Could it be that Mr. Graves, for instance, was an illustrator, and that Thorndyke had established his identity by looking through the works of all the well-known thick-line draughtsmen?

This problem occupied me for the rest of the day.  My explanation did not seem quite to fit Thorndyke’s description of his methods; but I could think of no other.  I turned it over during my solitary lunch; I meditated on it with the aid of several pipes in the afternoon; and having refreshed my brain with a cup of tea, I went forth to walk in the Temple gardens—­which I was permitted to do without breaking my parole—­to think it out afresh.

The result was disappointing.  I was basing my reasoning on the assumption that the pieces of reed were parts of a particular appliance, appertaining to a particular craft; whereas they might be the remains of something quite different, appertaining to a totally different craft or to no craft at all.  And in no case did they point to any known individual or indicate any but the vaguest kind of search.  After pacing the pleasant walks for upwards of two hours, I at length turned back towards our chambers, where I arrived as the lamp-lighter was just finishing his round.

My fruitless speculations had left me somewhat irritable.  The lighted windows that I had noticed as I approached had given me the impression that Thorndyke had returned.  I had intended to press him for a little further information.  When, therefore, I let myself into our chambers and found, instead of my colleague, a total stranger—­and only a back view at that—­I was disappointed and annoyed.

The stranger was seated by the table, reading a large document that looked like a lease.  He made no movement when I entered, but when I crossed the room and wished him “Good evening,” he half rose and bowed silently.  It was then that I first saw his face, and a mighty start he gave me.  For one moment I actually thought he was Mr. Weiss, so close was the resemblance, but immediately I perceived that he was a much smaller man.

I sat down nearly opposite and stole an occasional furtive glance at him.  The resemblance to Weiss was really remarkable.  The same flaxen hair, the same ragged beard and a similar red nose, with the patches of acne rosacea spreading to the adjacent cheeks.  He wore spectacles, too, through which he took a quick glance at me now and again, returning immediately to his document.