“He was fully eight feet from the casement, so that the assassin could not have reached in and struck him.  There were no footprints by the window, as the assassin had strapped small boards upon his feet.  It is most likely, therefore, that he has some peculiarity about his feet which he thought best to conceal.  He is about five feet five inches tall, weighs about one hundred and thirty-five pounds, and steps three or four inches longer when the right foot is thrown forward than he does when the left foot leads.  We have a cast of the assassin’s hand showing unmistakable evidence of the habit of biting the nails, with the exception of that of the little finger, which nail, by the way, is abnormally long, and could only have been spared for some special reason.  The murderer is most likely a foreigner.  His handwriting would indicate this even if we did not know, from the books he read, how conversant he is with at least one foreign tongue.  Again, he has some decided interest in the subject of cancers and, perhaps, some interest in legerdemain, if we may judge from his perusal of Robert Houdin’s book.

“There are one or two other things I have learned, but this, so far as any present effect is concerned, is about all we know, and it doesn’t seem to make the conduct of our search a very easy matter.  We have clearly to deal with a man who is possessed not merely of low criminal cunning, but, I have reason to believe, with one who has education and culture, and, if anything can be judged from handwriting, rare strength of character as well.  If we could only find some motive!  No one but a maniac would do such a deed without a motive, yet we can’t find one.  A maniac!  By Jove!  I hadn’t thought of that.  What do you think of the idea?  ’Though this be madness, yet there is method in’t,’ eh?”

I told him that the maniac theory did not appeal to me very strongly.  “Madness, to be sure, is often exceedingly cunning,” I said, “but it is hardly capable of such sustained masterfulness as our criminal has evinced.”

“Look here, Doc,” Maitland said, breaking out suddenly, “I’ve an idea.  Might not this fellow’s interest in cancers be due to his having one himself?  Suppose you make a canvass of the specialists on cancer in Boston and vicinity, and see if any of them remember being consulted by a patient answering the description with which I will provide you.  In addition to this I will insert an ad in the papers calling attention to a new method for the cure of cancer, and asking all interested to call at your office for further particulars.  The plan does not promise much, still it may bring him.  What do you say?”