“My first direct clew was the hammering that we heard in this house. It was too much to suppose that in two separate instances this hammering should be heard, and in each case Eva's father be present and no other discoverable agent, and that still he should have had nothing to do with it. Obviously, it must have been Herman Silber who did the hammering at Eva's home and here in this house. It was obvious, too, that Herman Silber was the ‘your own’ of the advertisement.
“To test Meyan, whom we found in the saloon, was not difficult. I arranged to have him overhear some one speaking of an arrest at Warsaw, which would at once suggest itself as a hotbed of Russian revolutionists to either a revolutionist or a police agent; but the idea would certainly give positive and very opposite reactions if the man were a true revolutionist or if he were a spy. Meyan's pulse so strengthened and slowed—as under a pleasurable stimulus—that I felt I had received confirmation of my suspicions, though I had not then the information which would enable me to expose the man. To secure this I sought out Dmitri Vasili. He introduced me to Munikov, who had been a friend of Silber before his imprisonment, and between them I got the history of Herman Silber and his daughter.
“I explained to Munikov and Vasili that the methods of the psychological laboratory would be as efficacious in picking out a spy as I have many times proved them to be in convicting the criminal.
“Every emotion reacts upon the pulse, which strengthens in joy and weakens in sorrow, grows slower with anger, faster with despair; and as every slightest variation is detected and registered by the Sphygmograph—I felt certain that if I could test the three men together by having Miss Silber tell her father's story aloud, I could determine conclusively by comparison of the records of the two revolutionists with that of Meyan, what his sympathies really were. I arranged with them to come here with me to-night, and after Meyan had arrived, they went as representatives of the revolutionary movement to ask his credentials.
“When he could furnish none, they proposed, and in fact forced him, into this test. It is a dangerous thing to endeavor to pass one's self off as a revolutionist, and it was safer for him to submit to a test than to have his mission frustrated by incurring not only their suspicion, but possibly death. Completely ignorant of the pitiless powers of psychological methods, and confiding in his steely nerves, which undoubtedly have carried him through many less searching ordeals, he agreed. You saw how perfectly he was able to control his face and every movement of his body while the test went on. But you can see here,” Trant spread out his strips of smoked paper, “on these records, which I shall preserve by passing them through a bath of varnish, how useless that self-control was, since the sphygmograph recorded by its moving stylus the hidden feelings of his heart.
“As I lay these side by side, you can see how consistently at each point in the story, Munikov and Vasili experienced the same feelings, but Meyan had feelings which were different. I did not dream, of course, when I started the test that I would discover in Meyan the same man who had betrayed Herman Silber. It was only when at her first mention of Valerian Urth I obtained from Meyan this startling and remarkable record,” he pointed to a place where the line suddenly had grown almost straight and flat, “that I realized that if the man before me was not himself Urth, he at least had some close and oppressive connection with him.
“Eva Silber had still the note that had been sent to summon her father on the errand of mercy which had caused his imprisonment.
“She gave it to me before you entered the room. I was certain that of all men in the world there was but one who could recognize or feel any emotion at sight of that yellowed and time-worn paper; and that man was Valerian Urth, who had used it to betray Herman Silber.
“I showed it to Meyan, and obtained this really amazing reaction which ends his record.” The psychologist pointed to the record. “It assured me that Meyan and Urth were one.”
“This is amazing, Mr. Trant,” Cuthbert Edwards said. “But you have left unexplained the most perplexing feature of all—the hammering!”
“To communicate with one another from their solitary cells, Russian prisoners long ago devised a code of spelling letters by knocking upon the wall—a code widely spread and known by every revolutionist. It is extremely simple; the letters of the alphabet,” Trant took from his pocket a slip of paper, “are arranged in this manner.”
He set down rapidly the alphabet, omitting two letters, arranged in four lines, thus:
| a | b | c | d | e | f |
| g | h | i | k | l | m |
| n | o | p | r | s | t |
| u | v | w | x | y | z |
“A letter is made,” the psychologist explained, “by giving first the proper number of knocks for the line, a short pause, then knocks for the number of the letter in the line. For instance, e is one knock and then five; y is four knocks and then five.
“By means of this code I translated the figures in the advertisement and obtained Meyan's name and address. I presume he used it not only in the advertisement, but at the office, because his long experience had taught him that Herman Silber, as many another man condemned to the horrors of a Russian prison for a term of years, had probably lost the power of speech, and continued to communicate, in freedom, by the means he had used for so many years in prison.”
“Wonderful, Mr. Trant, wonderful!” exclaimed Cuthbert Edwards. “I only regret that we can do nothing to Meyan; for there is no law, I think, by which he can be punished.”
The psychologist's face darkened.
“Vengeance is not ours,” he answered. “But I have given the key of Meyan's room to Munikov!”
The elder Edwards, clearing his throat, moved over toward Eva and put his arm about her. “Since you cannot go back to Russia,” he said awkwardly, “will you not let me welcome you into your place in my home?” And as the son sprang swiftly forward and caught his father's hand, Trant took up his instrument cases and went out alone into the warm April night.
The End
