"Isn't that exciting--a secret pa.s.sword," cried Jane enthusiastically.

"If you can manage it without compromising yourself too seriously, I wish you would make the young man's acquaintance."

"That will be simple," said Jane, remembering the admiring way in which he had raised his cup in her direction as she left the hotel.

"If possible find out who their visitors are in the apartment and keep your eyes open for any sort of signalling to the transports. If ever there is an opportunity to get hold of notes or mail delivered to either of them, don't hesitate to steam it open and copy it."

"Must I?" said Jane. "That hardly seems right or fair."

"Of course it's right," cried Mr. Fleck warmly. "Think of the lives of our soldiers that are at stake. The devilish ingenuity of these German spies must be thwarted at all costs. They seem to be able to discover every detail of our plans. Only two days ago one of our transports was thoroughly inspected from stem to stern. Two hours later twenty-six hundred soldiers were put aboard her on their way to France. Just by accident, as they were about to sail, a time-bomb was discovered in the coal bunkers, a bomb that would have sent them all to kingdom come."

"How terrible!"

"Somebody aboard is a traitor. Somebody knew when that inspection was made. Somebody put that bomb in place afterward. That shows you the kind of enemies we are fighting."

Jane shuddered. She was thinking of the sailing of another transport, the one that had carried her brother to France.

"Anything seems right after that," she said simply.

"Yes," said Mr. Fleck, "there is only one effective way to fight those spying devils. We must stop at nothing. They stop at nothing--not even murder--to gain their ends."

"I know that," said Jane hastily. "I saw something myself you ought to know about."

As briefly as she could she described the scene she had witnessed in the early morning hours from her bedroom window, the man following the younger Hoff, Hoff's discovery and pursuit of him around the corner and of his return alone.

"And in the morning," she concluded, "they found a man's body in the side street. He had a bullet through his heart. There was a revolver in his hand. The newspapers said that the police and the coroner were satisfied that it was a suicide. I caught a glimpse of Mr. Hoff's face when he came back from around that corner. It was all convulsed with hate, the most terrible expression I ever saw. I'm almost certain he murdered that man. I'm sure it wasn't a suicide."

"I'm sure, too, that it was no suicide," said Mr. Fleck gravely. "The man who was found there was one of my men, K-19, the man whose badge I have just given you. He had been detailed to shadow the Hoffs."

CHAPTER IV.

THE CLUE IN THE BOOK.

Subway pa.s.sengers sitting opposite Jane Strong as she rode up-town from Mr. Fleck's office, if they observed her at all--and most of them did--saw only a slim, good-looking young girl, dressed in a chic tailormade suit, crowned with a dashing Paris hat tilted at the proper angle to display best the sheen of her black, black hair, which after the prevailing fashion was pulled forward becomingly over her ears. Outwardly Jane was unchanged, but within her nerves were all atingle at the thought of the tremendous and fascinating responsibility so unexpectedly thrust upon her. Her mind, too, was aflame with patriotic ardor, but coupled with these new sensations was a persisting sense of dread, an intangible, unforgettable feeling of horror that kept cropping up every time her fingers touched the little metal disk in her purse.

The man who had carried it yesterday, the other "K-19" who had undertaken to shadow those people next door, now lay dead with a bullet through his heart. Was there, she wondered, a similar peril confronting her? Would her life be in danger, too? Was that the reason Mr. Fleck had told her of her predecessor's fate--to warn her how desperate were the men against whom she was to match her wits? Yet no sense of fear that projected itself into her busy brain as she cogitated over the task before her held her back. If anything she was rather thrilled at the prospect of meeting actual danger. What bothered her most was how she could best go about aiding Mr. Fleck and his men in their work.

Her opportunity came far more quickly than she had antic.i.p.ated. She had gotten off the train at the 96th Street station, purposing to walk the twenty odd blocks to her home as she pondered over the work that lay ahead of her. Busy with a horde of struggling new thoughts she proceeded along Broadway, for once in her life unheeding the rich gowns and feminine dainties so alluringly displayed in the shop windows. Suddenly she pulled herself together with a start. Directly ahead of her, plodding along in the same direction, was a figure that from behind seemed strangely familiar. She quickened her step until she caught up sufficiently with the man ahead to get a good glimpse of his side face. Nervously she caught her breath. Without any doubt it was the gray Van d.y.k.e beard of old Otto Hoff.

Where was he going? What was he doing? She paused and looked behind her, scanning the pavement on both sides of the street. She was half-hoping that she would discover Carter or some of his men shadowing their quarry, but her hope was vain. There was no one in the block at the moment but herself and Mr. Hoff. If Fleck's men had been watching his movements, the old man certainly seemed to have eluded them.

What should she do? Vividly there flashed into her mind her chief's parting words.

"Watch everything," he had charged her. "Remember everything, report everything. No detail is too unimportant. If you see one of the Hoffs leave the house, don't merely report to me that the old man or the young man left the house about three o'clock. That won't do at all. I want to know the exact time. Was it six minutes after three or eleven minutes after three? I must know what direction he went, if he was alone, how long he was absent, where he went, what he did, to whom he talked. Here in my office I take your reports, Carter's reports, a dozen other reports, and study them together. Things that in themselves seem trifling, unimportant, of no value, coupled with other seemingly unimportant trifles sometimes develop most important evidence."

To prove his point he had told her of the seemingly innocent wireless message that an operator, listening in, had picked up, at a time when Germans were still permitted to use the wireless station on Long Island for commercial messages to the Fatherland. On the face of it, it was the mere announcement of the death of a relative with a few details. But a little later the same operator caught the same message coming from another part of the country, with the details slightly different, and still later another message of the same purport. Evidently, by comparing the messages, the United States authorities had been able to work out a code.

Remembering this, Jane decided that it was her particular duty just now to follow the old German and note everything he did. For several blocks she trailed along behind him, without arousing any suspicion on his part that he was being followed. He stopped once to light a cigarette, the girl behind him diverting suspicion by hastily turning to a shop window. Again he stopped, this time before the display of viands in the window of a delicatessen store. Thoughtfully Jane noted the number, observing, too, that the name of the proprietor above the door was obviously Teutonic. She was half-expecting to see her quarry turn in here, but he walked on to the middle of the next block, where he entered a stationery store.

Hesitating but a second, to decide on a course of action, she followed him boldly into the store. She felt that she must ascertain just what he was doing in there. As she entered she saw that in the back part of the store was a lending library. Mr. Hoff had gone back to it and was inspecting the books displayed there. Unhesitatingly she, too, approached the book counter.

"Have you 'Limehouse Nights'?" she asked the attendant, naming the first book that came into her head. She had a copy of the book at home, but that seemed to be the only t.i.tle she could think of.

"We have several copies," the girl in charge answered, "but I think they are all out. I'll look."

As the clerk examined the shelves, Jane kept up a desultory talk with her, questioning her about various books on the shelves, all the while watching the old German out of the corner of her eye. His back was toward her, and he seemed to be examining various books on the shelves, turning over the pages as if unable to decide what he wanted. Curious as to what his taste in reading was, Jane endeavored to locate each book that he removed from its place, her idea being that she would later try to discover their t.i.tles. To her amazement she found that it was invariably the third book in each shelf that he removed and examined--the third from the end. It did not appear to her that he was examining the contents of the pages so much as searching them as if he expected to find something there.

All at once, as she furtively watched from behind him, she heard him give a little pleased grunt and she saw him picking out from between the leaves of the book a fragment of paper, which he held concealed in his hand. Watching closely, Jane saw him thrust this same hand into his trousers pocket, and when he brought it out she was certain that the hand was empty. What did this curious performance mean? What was the little slip of paper he had found in the book? Why had he concealed it in his pocket?

Still keeping her attention riveted on him, she picked up a book to mask her occupation and pretended to be turning its pages. She was glad she had done so, for a minute later old Hoff wheeled suddenly and looked sharply about him. Apparently having his suspicions disarmed by seeing only herself and the clerk there, he turned again to the bookshelves. Jane this time saw him thrust his fingers into his waistcoat pocket and withdraw therefrom,--she was almost certain of it,--a little slip of paper. She saw him remove from the second row of books the fifth from the end, open it quickly and close it again and then restore it to its place. As he did so he turned to leave the store.

"Didn't you find anything to read to-day, Mr. Hoff?" the clerk asked.

"Nodding," he answered. "You keep novels, trash, nodding worth while."

Her nerves aquiver, Jane waited until he was out of the store and then stepped briskly to the place where he had stood. Hastily she pulled forth the fifth book from the end in the second row. Turning its pages she came upon what she had antic.i.p.ated,--a strip of yellow manila paper,--the paper she was sure she had seen him take from his pocket. Hastily she examined it, expecting to find some message written there. To her chagrin it was just a meaningless jumble of figures in three columns.

534 5 2 331 54 6 644 76 3 49 12 9 540 30 12 390 3 2 519 3 6 327 20 2 97 Her first thought was to thrust the little sc.r.a.p of paper in her purse and start again in pursuit of old Hoff, but a sudden light began to dawn on her. This was a cipher message, of course. The old man had left it here for some one to come and get. If she followed Hoff, how was she to discover who the message was for? Puzzled as to what she should do, she borrowed a pencil from the clerk on the pretense of writing a postal and hastily copied the figures, after which she restored the slip to the book in which she had found it.

Glancing about undecidedly, wondering if it would do to take the clerk into her confidence, wishing she had some means of reaching Mr. Fleck and asking his advice, she spied in a drug-store just across the street a telephone booth. She could telephone from there and at the same time keep her eye on the store. Quickly she did so, twisting her head around all the time she was 'phoning to make sure that no one entered opposite.

"Is this Mr. Fleck?" she asked. "This is Miss Jones."

"So soon?" came back his voice. "What has happened? What is the matter? Have you changed your mind?"

"Not at all," she answered indignantly. "I've discovered something already--a cipher message."

"What's that?"

Even over the wire she could sense the eagerness in Mr. Fleck's tone, and a sense of achievement brought a radiant glow to her cheek.

"I ran into that man--you know whom--"

"The young one?" he interrupted.

"No, the uncle."

"Yes, yes, go on," cried Mr. Fleck impatiently.

"I followed him along Broadway after I got off at 96th Street and into a library and stationery store. I watched him fuss over the books there, and I think he got a slip of paper with a message out of one of them."

"Good," cried Mr. Fleck, "that is something new. Go on."

"And then he slipped a paper into a book--"

"Did you notice what book?"

"I don't know the t.i.tle. It was the fifth book from the end on the second shelf, and I got the paper and copied it."

"Splendid. What did the message say?"

"It's just a lot of figures. I put it back after copying it, and I am in a drug-store across the street where I can watch to see if any one comes to get the message. What shall I do now?"

"Can you remain there fifteen minutes without arousing suspicion?"

"Certainly. I'll say I am waiting for some one."

"Good. I'll get in touch with Carter at once. He'll tell you what to do when he arrives."

Impatiently Jane sat there, keeping vigilant watch on the entrance across the street, determined to be able to describe minutely each person that entered. From time to time she surrept.i.tiously studied the postcard on which she had jotted down the mysterious numbers. How utterly meaningless they looked. Surely it would be impossible for any one, even Mr. Fleck, to decipher any message that these figures might convey. It would be impossible unless one had the key. Figures could be made to mean anything at all. She doubted if her discovery could be of much importance after all, yet certainly Mr. Fleck had seemed quite excited about it.

She spied Carter pa.s.sing in a taxi. Two other men were with him. Her first impulse was to run out in the street and signal to him, but she waited, wondering what she should do. She was glad she had not acted impulsively, for a moment later Carter entered alone, evidently having left the car somewhere around the corner. She expected that he would address her at once, but that was not Carter's way. He went to the soda counter and ordered something to drink, his eyes all the while studying his surroundings. Presently he pretended to discover her sitting there. To all appearances it might have been an entirely casual meeting of acquaintances.

"Good-morning, Miss Jones," he said quite cordially, extending his hand. "I'm lucky to have met you, for my daughter gave me a message for you."

He put just a little stress on the words "my daughter" and Jane understood that he was referring to "Mr. Fleck."

"Indeed," she replied, "what is it?"

"She wants you to go down-town at once and meet her at Room 708--you know the building."

"Aren't you coming, too?"

"Not right away. I have some errands to do in the neighborhood. I've got to buy a book for a birthday present. There's a library around here somewhere, isn't there?"

"Just across the street," said Jane, entering into the spirit of the masked conversation with interest. "I was looking at a fine book over there a few minutes ago. You'll find it on the second shelf--the fifth book from the end, on the north side of the store."

"I'll remember that," said Carter, repeating, "the fifth book on the second shelf."

"That's right," said Jane, as they left the drug-store together.

"Which way did the old man go?" asked Carter.

"Down Broadway--toward home," she replied. "I wanted to follow him, but it seemed more important to stay here and watch to see if any one came for the message he left there in the book."

"You did just right, and the Chief is tickled to death. He wants to see you right away. You have a copy of the message, haven't you?"

"Yes, do you wish to see it?"

"No, but he does. Has anybody entered the store since you were there?"

"n.o.body, that is no one but a couple of girls."

"What did they look like? Describe them."

"Why," Jane faltered, "I did not really notice. I was not looking for girls. I was watching to see that no other men entered the store."

Carter shook his head.

"You ought to have spotted them, too. You never can tell who the Germans will employ. They have women spies, too,--clever ones."

"I never thought of their using girls," protested Jane.

"Humph," snapped Carter, "ain't we using you? Ain't one of our best little operatives right this minute working in a nursegirl's garb pulling a baby carriage with a baby in it up and down Riverside Drive? Well, it can't be helped. You'd better beat it down-town to the Chief right away."

"I'll take a subway express," said Jane, feeling somewhat crestfallen at his implied suggestion of failure.

Twenty-five minutes later found her once more in Mr. Fleck's office. Thrilling with the excitement of it all she told him in detail how she had followed old Hoff and of his peculiar actions in the bookstore.

"And here," she said, presenting the postcard, "is an exact copy of the cipher message he left there. I copied every figure, in the columns, just as they were set down. I don't suppose though you'll be able to make head or tail out of it. I know I can't."

"Don't be too sure of that," smiled Chief Fleck, as he took the card. "When you get used to codes, most of them identify themselves at the first glance--at least they tell what kind of a code it is. That's one thing about the Germans that makes their spy work clumsy at times. They are so methodical that they commit everything to writing. Now the most important things I know are right in here"--he tapped his head. "Every once in a while they ransack my rooms, but they never find anything worth while. Now this code"--he was studying the card intently--"seems to be one of a sort that our friends from Wilhelmstra.s.se are ridiculously fond of using. It is manifestly a book code."

"A book code," Jane repeated perplexedly. "I don't understand."

"It is very simple when two persons who wish to communicate with each other secretly both have a copy of some book they have agreed to use. They write their message out and then go through the book locating the words of the message by page, line and word. That's what the three columns mean. Our only problem is to discover which is the book they both have. They often employ the Bible or a dictionary or--"

He stopped abruptly and studied the columns of figures.

"This code," he went on, "on its face is from a book that has at least 544 pages. One of the pages has at least 76 lines--that's the middle column--so the book must be set in small type."

"What book do you suppose it is?" asked Jane interestedly. She was glad now that she had listened to Carter. She was sure she was going to like being in the service. It was all so interesting, and she was learning so many fascinating things.

"If my theory is right those letters indicate that the book used was an almanac. That's the book that Wilhelmstra.s.se made use of when a wireless message was sent in cipher to the German amba.s.sador directing him to warn Americans not to sail on the Lusitania. They betrayed themselves at the Emba.s.sy by sending out to buy a copy of this almanac. Let's see how our theory works out."

Taking up an almanac that lay on his desk he began turning to the pages indicated in the first column of figures, checking off the lines indicated in the second column and putting a ring around the words marked by the third column of figures.

"Let's see--page 534--fifth line--second word--that's (eight). Now then--page 331--that's the chronology of the war in the almanac, so I guess we are on the right track--fifty-fourth line--sixth word--(transport)."

"Isn't it wonderful!" cried Jane.

"d.a.m.n them," he exploded. "I know we are on the right track. Some transports with our troops sailed this morning, and already the German spies are spreading the news, hoping to get it to one of their unspeakable U-boats."

Quickly he ran through the rest of the cipher, writing it out as he went along: EIGHT--TRANSPORT--SAILED--THURSDAY--15,000--INFANTRY--FIVE DESTROYERS.

As Fleck finished the message his face became almost black with rage.

"d.a.m.n them," he cried again, "in spite of everything we do they get track of all our troop movements. Their information, whenever we succeed in intercepting it, is always accurate. If I had my way I'd lock up every German in the country until the war was over, and I'd shoot a lot of those I locked up. Until the whole country realizes that we are living in a nest of spies--that there are German spies all around us, in every city, in every factory, in every regiment, on every ship, everywhere right next door to us--this country never can win the war."

"What does the '97' at the end mean?" questioned Jane timidly, a little bit frightened at his outburst, yet more than ever realizing the vast importance of his work--and hers.