"I have an important message for you. I am a French spy. I must get this message to you. Answer me in some way. Heave a big yawn or clear your throat and I'll know you hear me and get what I'm saying. I merely want to make sure you are what I think you are. I don't dare reveal myself to you for fear that I may be mistaken and you'd turn me over to the government."
These words were tapped off, alphabetically, with a small instrument, probably a pencil, on the window overlooking a court inclosed by the building on three sides. After a pause of half a minute, following the appeal just recorded, the dot-and-dash tapping continued thus:
"I am looking through the shade of your window and can see that you are listening attentively; so you need not reply. Just continue to listen, and I shall know everything is all right.
"When you leave for America you will be supplied with a message in cipher, prepared by me, for a certain agent of the kaiser. That message will bear the appearance of having been written by a friend of yours to you, but it will contain information in invisible ink for your benefit as a loyal agent of the Allies. This information will be of great value to the Allies, supplying them with material for undermining the Teutonic spy system in England, France, and America, which recently declared war.
"This is all. I merely wished to advise you of what you will find written with invisible ink on the paper that will be placed in your possession when you set out on your return to America."
The tapping ceased. Irving remained like a statue in his chair for several minutes. Then he arose, went to the window and pulled the shade aside. The court was dark, save for a solitary dim light out at the entrance. He could just faintly discern the steel structure of the fire escape near the window.
"That's the way he got up," he half muttered. "He stood there on that landing while he tapped his message. I wonder who he is and how he spotted me. He must be a very clever fellow. I really believe he's what he represented himself to be; and yet, it may possibly be a trap to catch me. However, I don't see what I can do except await developments."
He went to bed and slept better than might have been expected under the circumstances. But he had become so used to critical situations by this time that he felt almost capable of sleeping peacefully on the "edge of the earth" with a torpedo for a pillow.
Next day the mystery of the window-telegraph spy bothered him a good deal, even more than it did immediately after the fellow had "dotted and dashed" his message on the pane of glass.
"I wonder who he was?" he repeated many times. "I wonder if he's somebody I'm in close touch with every day?"
The suggestion caused him to watch narrowly every person in the office with whom he did business for the German government. But the more he watched, the more unsatisfactory the situation became. He continued his furtive outlook several days, but finally admitted to himself that the prospect of his efforts solving the mystery was anything but bright.
Meanwhile the spy's preparations for a new excursion out into a broad field of international espionage were rapidly drawing to a close. The surgeon at the hospital who had performed the skin-grafting operation on his arm pronounced it sufficiently well healed, first, to warrant taking the limb out of the sling, and then, a week later, for the removal of the bandage. There were a few slightly rough places here and there. around the edges of the patch, and one small scar at the lower end of the middle strip of skin where it had been twisted to cause it to lie "right side out" through the middle of the larger patch and make the latter complete by meeting the outer edges that had been undercut and drawn to it.
All things considered, Irving was well pleased with the course of events during his sojourn in the German capital. Although a number of situations had developed with rather dangerous aspect, he had pulled through all of them with apparent success. While he was still reporting daily at the hospital for the dressing of his arm his lieutenancy commission was acted upon in the war office and was delivered to him through Mr. Herrmann.
At last the day arrived for a windup of the young spy's affairs in the intelligence offices, and he was summoned into the presence of "the baron" and Superintendent Herrmann. A third man also was present to receive the young espionage student. He wore a navy uniform and was introduced as Capt. Bartholf of the submarine service.
"You will go with Capt. Bartholf on board his boat," "the baron" announced, addressing "Lieut. Hessenburg." "He will land you on the coast of Spain and from there you will go to a German consul and devise a method for getting you to Mexico and from there into the United States.
"By the way," the high intelligence official remarked, suddenly interrupting himself and addressing Superintendent Herrmann; "how about that letter that was being prepared for Lieut. Hessenburg to take along?"
"I'll see," replied Herrmann, as he started for the door.
"Bring Strauss in with you," "the baron" called after him. "I may want to ask him some questions."
"Strauss!"
The name echoed in Irving's brain with a succession of significant thrills. What did Strauss have to do with the preparation of the letter he was to take with him? Was it possible--?
He did not finish the sentence in words, but the idea was there and remained uppermost in his mind during the remainder of the session in "the baron's" office. Presently Herrmann returned, accompanied by the card-catalog expert, who carried an envelope of ordinary business-correspondence size in one hand. This envelope he laid on the desk in front of the intelligence chief.
The latter picked it up, looked keenly at Strauss and asked with like sharpness of voice:
"This paper was prepared entirely by you, was it?"
"Yes," the cataloger answered.
"And it has been in no other person's hands at any time since you began work on it?"
"No."
"And you vouch for the accuracy and thoroughness of its preparation?"
"Yes."
"That's all. You may retire."
Strauss left the room. "The baron" turned to Irving, handed him the letter, and said:
"This innocent looking missive is of vast importance. It is addressed in cipher to a very important person in America who is high in the confidence of the United States government. You have learned how to read this cipher and will work it out for yourself. That is all. Good-by. I wish you a continuation of the success that has been yours in a remarkable degree heretofore."
Irving took "the baron's" offered hand and then left the office accompanied by Capt. Bartholf. As he went the name of Strauss continued to ring in his head, together with this startling conviction:
The catalog expert was the French spy who had tapped the "telegraph message" on his window at the rooming house!