Avery Knight, sat lost in thought for a while. At length he looked up brightly.

“Doc,” said he, “I have it. Put on your hat, and come with me. In half an hour I guarantee that you shall stand in the presence of Shamrock Jolnes.”

I entered a cab with Avery Knight. I did not hear his instructions to the driver, but the vehicle set out at a smart pace up Broadway, turning presently into Fifth Avenue, and proceeding northward again. It was with a rapidly beating heart that I accompanied this wonderful and gifted assassin, whose analytical genius and superb self-confidence had prompted him to make me the tremendous promise of bringing me into the presence of a murderer and the New York detective in pursuit of him simultaneously. Even yet I could not believe it possible.

“Are you sure that you are not being led into some trap?” I asked. “Suppose that your clue, whatever it is, should bring us only into the presence of the Commissioner of Police and a couple of dozen cops!”

“My dear doctor,” said Knight, a little stiffly. “I would remind you that I am no gambler.”

“I beg your pardon,” said I. “But I do not think you will find Jolnes.”

The cab stopped before one of the handsomest residences on the avenue. Walking up and down in front of the house was a man with long red whiskers, with a detective’s badge showing on the lapel of his coat. Now and then the man would remove his whiskers to wipe his face, and then I would recognize at once the well-known features of the great New York detective. Jolnes was keeping a sharp watch upon the doors and windows of the house.

“Well, doctor,” said Knight, unable to repress a note of triumph in his voice, “have you seen?”

“It is wonderful—wonderful!” I could not help exclaiming as our cab started on its return trip. “But how did you do it? By what process of induction—”

“My dear doctor,” interrupted the great murderer, “the inductive theory is what the detectives use. My process is more modern. I call it the saltatorial theory. Without bothering with the tedious mental phenomena necessary to the solution of a mystery from slight clues, I jump at once to a conclusion. I will explain to you the method I employed in this case.