“Very well, then.  To-night at eight I shall be there,” promised Kennedy, as the novelist and he shook hands.

“What do you think of the Revalenko story?” I asked of Craig, as we started uptown again.

“Anything is possible in this case,” he answered sententiously.

“Well,” I exclaimed, “this all is truly Russian.  For intrigue they are certainly the leaders of the world to-day.  There is only one person that I have any real confidence in, and that is old Saratovsky himself.  Somebody is playing traitor, Craig.  Who is it?”

“That is what science will tell us to-night,” was his brief reply.  There was no getting anything out of Craig until he was absolutely sure that his proofs had piled up irresistibly.

Promptly at eight we met at the old house on Fifth Avenue.  Kharkoff’s wounds had proved less severe than had at first been suspected, and, having recovered from the shock, he insisted on being transferred from the hospital in a private ambulance so that he could be near his friends.  Saratovsky, in spite of his high fever, ordered that the door to his room be left open and his bed moved so that he could hear and see what passed in the room down the hall.  Nevsky was there and Kazanovitch, and even brave Olga Samarova, her pretty face burning with the fever, would not be content until she was carried upstairs, although Dr. Kharkoff protested vigorously that it might have fatal consequences.  Revalenko, an enigma of a man, sat stolidly.  The only thing I noticed about him was an occasional look of malignity at Nevsky and Kazanovitch when he thought he was unobserved.

It was indeed a strange gathering, the like of which the old house had never before harboured in all its varied history.  Every one was on the qui vive, as Kennedy placed on the table a small wire basket containing some test-tubes, each tube corked with a small wadding of cotton.  There was also a receptacle holding a dozen glass-handled platinum wires, a microscope, and a number of slides.  The bomb, now rendered innocuous by having been crushed in a huge hydraulic press, lay in fragments in the box.

“First, I want you to consider the evidence of the bomb,” began Kennedy.”  No crime, I firmly believe, is ever perpetrated without leaving some clue.  The slightest trace, even a drop of blood no larger than a pin-head, may suffice to convict a murderer.  The impression made on a cartridge by the hammer of a pistol, or a single hair found on the clothing of a suspected person, may serve as valid proof of crime.

“Until lately, however, science was powerless against the bomb-thrower.  A bomb explodes into a thousand parts, and its contents suddenly become gaseous.  You can’t collect and investigate the gases.  Still, the bomb-thrower is sadly deceived if he believes the bomb leaves no trace for the scientific detective.  It is difficult for the chemist to find out the secrets of a shattered bomb.  But it can be done.