"What do you make of that?" inquired Carton half an hour later as he met us breathlessly at the laboratory.

He unfolded a letter over which he had evidently been puzzling considerably. It was written, or rather typewritten, on plain paper. The envelope was plain and bore no marks of identification, except possibly that it had been mailed uptown.

The letter ran:

DEAR SIR:

Although this is an anonymous letter, I beg that you will not consider it such, since it will be plain to you that there is good reason for my wishing to remain nameless.

I want to tell you of some things that have taken place recently at a little hotel in the West Fifties. No doubt you know of the place already—the Little Montmartre.

There are several young and wealthy men who frequent this resort. I do not dare tell you their names, but one is a well-known club-man and man about town, another is a banker and broker, also well known, and a third is a lawyer. I might also mention an intimate friend of theirs, though not of their position in society—a doctor who has somewhat of a reputation among the class of people who frequent the Little Montmartre, ready to furnish them with anything from a medical certificate to drugs and treatment.

I have read a great deal in the newspapers lately of the disappearance of Betty Blackwell, and her case interests me. I think you will find that it will repay you to look into the hint I have given. I don't think it is necessary to say any more. Indeed it may be dangerous to me, and I beg that you will not even show this letter to anyone except those associated with you and then, please, only with the understanding that it is to go no farther.

Betty Blackwell is not at this hotel, but I am sure that some of those whose wild orgies have scandalized even the Little Montmartre know something about her.

Yours truly,
AN OUTCAST.

Kennedy looked up quickly at Carton as he finished reading the letter.

"Typical," he remarked. "Anonymous letters occasionally are of a friendly nature, but usually they reflect with more or less severity upon the conduct or character of someone. They usually receive little attention, but sometimes they are of the most serious character. In many instances they are most important links in chains of evidence pointing to grave crimes.

"It is possible to draw certain conclusions from such letters at once. For instance, it is a surprising fact that in a large number of cases the anonymous letter writer is a woman, who may write what it does not seem possible she could write. Such letters often by their writing, materials used, composition and general form indicate at once the sex of the writer and frequently show nationality, age, education, and occupation. These facts may often point to the probable author.

"Now in this case the writer evidently was well educated. Assumed illiteracy is a frequent disguise, but it is impossible for an author to assume a literacy he or she does not possess. Then, too, women are more apt to assume the characteristics of men than men of women. There are many things to be considered. Too bad it wasn't in ordinary handwriting. That would have shown much more. However, we shall try our best with what we have here. What impressed you about it?"

"Well," remarked Carton, "the thing that impressed me was that as usual and as I fully expected, the trail leads right back to protected vice and commercialized graft. This Little Montmartre is one of the swellest of such resorts in the city, the legitimate successor to the scores and hundreds of places which the authorities and the vice investigators have closed recently. In fact, Kennedy, I consider it more dangerous, because it is run, on the surface at least, just like any of the first-class hotels. There's no violation of law there, at least not openly."

Craig had continued to examine the letter closely. "So, you have already investigated the Little Montmartre?" he queried, drawing from his pocket a little strip of glass and laying it down carefully over the letter.

"Indeed I have," returned the District Attorney, watching Kennedy curiously. "It is a place with a very unsavoury reputation. And yet I have been able to get nothing on it. They are so confounded clever. There is never any outward violation of law; they adhere strictly to the letter of the rule of outward decency."

Over the typewritten characters Kennedy had placed the strip of glass and I could see that it was ruled into little oblongs, into each of which one of the type of the typewritten sheet seemed to fall. Apparently he had forgotten the contents of the letter in his interest in the text itself. He held the paper up to the light and seemed to study its texture and thickness. Then he examined the typed characters more closely with a little pocket magnifying glass, his lips moving as if he were counting something. Next he seized a mass of correspondence on his desk and began comparing the letter with others, apparently to determine just the shade of writing of the ribbon. Finally he gave it up and leaned back in his chair regarding us.

"It is written in the regular pica type," he remarked thoughtfully, "and on a machine that has seen considerable rough usage, although it is not an old machine. It will take me a little time to identify the make, but after I have done that, I think I could identify the particular machine itself the moment I saw it. You see, it is only a clue that would serve to fix it once you found that machine. The point is, after all, to find it. But once found, I am sure we shall be close to the source of the letter. I may keep this and study it at my leisure?"

"Certainly."

For a moment Carton was silent. Then it seemed as though the matter of
Betty Blackwell brought to mind what he had read in the morning papers.

"That robbery of Langhorne's safe was a most peculiar thing, wasn't it?" he meditated. "I suppose you know what Miss Blackwell was?"

"Langhorne's stenographer and secretary, of course," I replied quickly.

"Yes, I know. But I mean what she had actually done? I don't believe you do. My county detectives found out only last night." Kennedy paused in his rummaging among some bottles to which he had turned at the mention of the safe robbery. "No—what was it?" he asked.

Carton bent forward as if our own walls might have ears and said in a low voice: "She was the operator who took down the detectaphone conversations at the other end of the wire in a furnished room in the house next to Gastron's."

He drew back to see what effect the intelligence had on us, then resumed slowly: "Yes, I've had my men out on the case. That is what they think. I believe she often executed little confidential commissions for Langhorne, sometimes things that took her on short trips out of town. There is a possibility that she may be on a mission of that sort. But I think—it's this Black Book case that involves her now."

"Langhorne wouldn't talk much about anything," I put in, hastily remembering his manner. "He may not be responsible—but from his actions I'd wager he knows more about her than appears."

"Just so," agreed Carton. "If my men can find out that she was the operator who 'listened in' and got the notes and the transcript of the Black Book, then she becomes a person of importance in the case and the fact must be known to others who are interested. Why," he pursued, "don't you see what it means? If she is out of the way, there is no one to swear to the accuracy of the notes in the record, no one to identify the voices—even if we do manage finally to locate the thing."

"Dorgan and the rest are certainly leaving nothing undone to shake the validity of the record," ruminated Kennedy, accepting for the moment at least Carton's explanation of the disappearance of Miss Blackwell. "Have you any idea what might have happened to her?"

Carton shook his head negatively. "There are several explanations," he replied slowly. "As far as we have been able to find out she led a model life, at home with her mother and sister. Except for the few commissions for Langhorne and lately when she was out rather late taking the detectaphone notes, she was very quiet,—in fact devoted to her mother and the education of her younger sister."

"What sort of place was it in which the receivers of the detectaphone were located—do you know?" asked Kennedy quickly.

"Yes, it seems to be a very respectable boardinghouse," answered Carton. "She came there with a grip about a week ago and hired a room, saying she was out of town a great deal. Just about the same time a young man, who posed as a student in electrical engineering at some school uptown, left. It must have been he who installed the detectaphone—perhaps with the aid of a waiter in Gastron's. At any rate, she seems to have been alone in the boarding-house—that is, I mean, not acquainted with any of the other guests—during the time when she was taking down the record. Dorgan traced the wires, outside the two buildings, to her rooms, but she was not there. In fact there was nothing there but a grip with a few articles that give no clue to anything. Somehow she must have heard of it, for no one knows anything about her, since then."

"Perhaps Langhorne is keeping her out of the way so that no one can tamper with her testimony," I suggested.

"It's possible," said Carton in a tone that showed that he did not believe in that explanation. "How about that safe robbery, Kennedy? Some of the papers hinted that she might have known something of that. I had a man down there watching, afterwards, but I had cautioned him to be careful and keep under cover. One of the elevator boys told him that the robbers had made a hole in the safe. What did he mean? Did you see it?"

Rapidly Kennedy sketched what we had done, telling the story of how the dynamometer had at least partly exonerated Betty Blackwell.

When he reached the description of the hole in the safe, Carton was absolutely incredulous. As for myself, it presented a mystery which I found absolutely inexplicable. How it was possible in such a short time to make a hole in a safe by any known means, I could not understand. In fact, if I had not seen it myself, I should have been even more sceptical than Carton.

Kennedy, however, made no reply immediately to our expressions of doubt. He had found and set apart from the rest a couple of little glass bottles with ground glass stoppers. Then he took a thick piece of steel and laid it across a couple of blocks of wood, under which was a second steel plate.

Without a word of explanation, he took the glass stopper out of the larger bottle and poured some of the contents on the upper plate of steel. There it lay, a little mound of reddish powder. Then he took a little powder of another kind from the other bottle.

He lighted a match and ignited the second pile of powder.

"Stand back—close to the wall—shield your eyes," he called to us.

He had dropped the burning mass on the red powder and in two or three leaps he joined us at the far end of the room.

Almost instantly a dazzling, intense flame broke out. It seemed to sizzle and crackle. With bated breath we waited and, as best we could, shielding our eyes from the glare, watched.

It was almost incredible, but that glowing mass of powder seemed literally to be sinking, sinking right down into the cold steel. In tense silence we waited. On the ceiling we could see the reflection of the molten mass in the cup which it had burned for itself in the cold steel plate.

At last it fell through to the lower piece of steel, on which it burnt itself out—fell through as the burning roof of a frame building might have fallen into the building.

Neither Carton nor I spoke a word, but as we now cautiously advanced with Kennedy and peered over the steel plate we instinctively turned to Craig for an explanation. Carton seemed to regard him as if he were some uncanny mortal. For, there in the steel plate, was a hole. As I looked at the clean-cut edges, I saw that it was smaller but identical in nature with that which we had seen in the safe in Langhorne's office.

"Wonderful!" ejaculated Carton. "What is it?"

"Thermit," was all Kennedy said, as just a trace of a smile of satisfaction flitted over his face.

"Thermit?" echoed Carton, still as mystified as before.

"Yes, an invention of a chemist named Goldschmidt, of Essen, Germany. It is composed of iron oxide, such as conies off a blacksmith's anvil or the rolls of a rolling-mill, and powdered metallic aluminum. You could thrust a red-hot bar into it without setting it off, but when you light a little magnesium powder and drop it on thermit, a combustion is started that quickly reaches fifty-four hundred degrees Fahrenheit. It has the peculiar property of concentrating its heat to the immediate spot on which it is placed. It is one of the most powerful oxidizing agents known, and it doesn't even melt the rest of the steel surface. You see how it ate its way directly through this plate. Steel, hard or soft, tempered, annealed, chrome, or Harveyized—it all burns just as fast and just as easily. And it's comparatively inexpensive, also. This is an experiment Goldschmidt it fond of showing his students—burning holes in one—and two-inch steel plates. It is the same with a safe—only you need more of the stuff. Either black or red thermit will do the trick equally well, however."

Neither of us said anything. There was nothing to say except to feel and express amazement.

"Someone uncommonly clever or instructed by someone uncommonly clever, must have done that job at Langhorne's," added Craig. "Have you any idea who might pull off such a thing for Dorgan or Murtha?" he asked of Carton.

"There's a possible suspect," answered Carton slowly, "but since I've seen this wonderful exhibition of what thermit can do, I'm almost ashamed to mention his name. He's not in the class that would be likely to use such things."

"Oh," laughed Kennedy, "never think it. Don't you suppose the crooks read the scientific and technical papers? Believe me, they have known about thermit as long as I have. Safes are constructed now that are proof against even that, and other methods of attack. No indeed, your modern scientific cracksman keeps abreast of the times in his field better than you imagine. Our only protection is that fortunately science always keeps several laps ahead of him in the race—and besides, we have organized society to meet all such perils. It may be that the very cleverness of the fellow will be his own undoing. The unusual criminal is often that much the easier to run down. It narrows the number of suspects."

"Well," rejoined Carton, not as confident now as when he had first met us in the laboratory, "then there is a possible suspect—a fellow known in the underworld as 'Dopey' Jack—Jack Rubano. He's a clever fellow—no doubt. But I hardly think he's capable of that, although I should call him a rather advanced yeggman."

"What makes you suspect him?" asked Kennedy eagerly.

"Well," temporized Carton, "I haven't anything 'on' him in this connection, it's true. But we've been trying to find him and can't seem to locate him in connection with primary frauds in Murtha's own district. Dopey Jack is the leader of a gang of gunmen over there and is Murtha's first lieutenant whenever there is a tough political battle of the organization either at the primaries or on Election Day."

"Has a record, I suppose?" prompted Kennedy.

"Would have—if it wasn't for the influence of Murtha," rejoined Carton.

I had heard, in knocking about the city, of Dopey Jack Rubano. That was the picturesque title by which he was known to the police and his enemies as well as to his devoted followers. A few years before, he had begun his career fighting in "preliminaries" at the prize fight clubs on the lower East Side.

He had begun life with a better chance than most slum boys, for he had rugged health and an unusually sturdy body. His very strength had been his ruin. Working decently for wages, he had been told by other petty gang leaders that he was a "sucker," when he could get many times as much for boxing a few rounds at some "athletic" club. He tried out the game with many willing instructors and found that it was easy money.

Jack began to wear better clothes and study the methods of other young men who never worked but always seemed to have plenty of money. They were his pals and showed him how it was done. It wasn't long before he learned that he could often get more by hitting a man with a blackjack than by using his fists in the roped ring. Then, too, there were various ways of blackmail and extortion that were simple, safe, and lucrative. He might be arrested, but he early found that by making himself useful to some politicians, they could fix that minor difficulty in the life.

Thus because he was not only strong and brutal, but had a sort of ability and some education, Dopey Jack quickly rose to a position of minor leadership—had his own incipient "gang," his own "lobbygows." His following increased as he rose in gangland, and finally he came to be closely associated with Murtha himself on one hand and the "guns" and other criminals of the underworld who frequented the stuss games, where they gambled away the products of their crimes, on the other.

Everyone knew Dopey Jack. He had been charged with many crimes, but always through the aid of "the big fellows" he avoided the penitentiary and every fresh and futile attempt to end his career increased the numbers and reverence of his followers. His had been the history and he was the pattern now of practically every gang leader of consequence in the city. The fight club had been his testing ground. There he had learned the code, which can be summarized in two words, "Don't squeal." For gangland hates nothing so much as a "snitch." As a beginner he could be trusted to commit any crime assigned to him and go to prison, perhaps the chair, rather than betray a leader. As a leader he had those under him trained in the same code. That still was his code to those above him in the System.

"We want him for frauds at the primaries," repeated Carton, "at least, if we can find him, we can hold him on that for a time. I thought perhaps he might know something of the robbery—and about the disappearance of the girl, too.

"Oh," he continued, "there are lots of things against him. Why, only last week there was a dance of a rival association of gang leaders. Against them Dopey Jack led a band of his own followers and in the ensuing pistol battle a passer-by was killed. Of course we can't connect Dopey Jack with his death, but—then we know as well as we know anything in gangland that he was responsible."

"I suppose it isn't impossible that he may know something about the disappearance of Miss Blackwell," remarked Kennedy.

"No," replied Carton, "not at all, although, so far, there is absolutely no clue as far as I can figure out. She may have been bought off or she may have been kidnapped."

"In either case the missing girl must be found," said Craig. "We must get someone interested in her case who knows something about what may happen to a girl in New York."

Carton had been revolving the matter in his mind. "By George," he exclaimed suddenly, "I think I know just the person to take up that case for us—it's quite in her line. Can you spare the time to run down to the Reform League headquarters with me?"

"Nothing could be more important, just at the minute," replied Craig.

The telephone buzzed and he answered it, a moment later handing the receiver to Carton.

"It's your office," he said. "One of the assistant district attorneys wants you on the wire."

As Carton hung up the receiver he turned to us with a look of great satisfaction.

"Dopey Jack has just been arrested," he announced. "He has shut up like an oyster, but we think we can at least hold him for a few days this time until we sift down some of these clues."