It was not until the middle of the afternoon that there came a sudden, brief message from the Secret Service in Washington:

Mr. Craig Kennedy,
New York.

I have located the Baroness Von Dorf in a private sanitarium here and will have her in New York tonight by eight o'clock.

Burke.

"In a private sanitarium—will have her in New York tonight," reread Craig, studying the message. "Then it wouldn't seem that there could be much the matter with her."

For a few moments he paced the laboratory floor, alternately studying the boards and the yellow telegram. At last, his face seemed to light up as if he had reasoned something out to his satisfaction. Quickly he reached for the telephone and called Dr. Leslie.

"I shall have the Baroness here tonight at eight, Leslie," I heard him say. "Don't tell a soul about it. But I'd like to have you make all the arrangements to secure the attendance of Haynes, Ames, and Madame Dupres here just a bit ahead of that time."

There was nothing that I could do to aid Craig more in the hours that remained than to efface myself, and I did it in the most effectual way I could think of, compatible with my interest in the case. I rode down to Dr. Leslie's office and dined hurriedly with him. The only new information I gleaned was that Haynes had visited him during the afternoon and had outlined his theory of cyanogen, which certainly seemed to me to fit in quite readily with the facts.

When we reached the laboratory, early, Kennedy was still absorbed in studying his microscope. He said nothing, but apparently had gained an air of confidence which he lacked the night before.

The Baroness had not yet arrived, but a few minutes after us came Ashby Ames, still complaining about the closing of his apartment and the inconvenience the whole affair had put him to. Haynes arrived and Ames cut short his tirade, glancing resentfully at the veterinary as though in some way he were responsible for his troubles. Madame Dupres arrived shortly, and I could not help noticing that Haynes was patently jealous of even the nod of recognition she gave to Ames.

"I don't think I need say that this is one of the most baffling cases that we have ever had," began Kennedy, with a glance at Dr. Leslie.

"It certainly is," chimed in the coroner, as though he had been appealed to for corroboration.

"In the first place," resumed Kennedy, "I discovered in the air up there in Delaney's room just a trace of cyanogen."

Haynes nodded approvingly, glancing from one to the other of us.

"But," added Craig, as if he had built up a house of cards merely to demolish it, "I don't think that cyanogen was the cause of Delaney's death—although it furnished the clew."

"What could it have been, then?" demanded Haynes, his face clouding.

Kennedy looked at him calmly. "You've heard of anthrax?" he asked simply.

"Y-yes," replied Haynes, meeting his eye fixedly. "Murrain—the cattle disease."

"That is so deadly to human beings sometimes," added Craig. "Well, I've found something very much like anthrax germs in the sweepings that I took up with the vacuum cleaner up there."

Dr. Leslie was listening intently.

"I can't see how it could have been anthrax," he put in, slowly shaking his head. "Why, Kennedy, the symptoms were entirely different."

"No, this was a poisoning of some kind," added Dr. Haynes. "Dr. Leslie himself tells me that you found traces of cyanogen in the air—and you have just said so, too."

Kennedy indicated the microscope. "Take a look at that slide under the lens," he said simply.

I was nearest and as he evidently meant each of us to look, I did so. Under the high-power lens I could see some little roundish dots moving slowly through the field.

Haynes looked next. "But, Professor Kennedy," he objected, almost as soon as he had time for a good look, "the bacilli of anthrax have normally the form of straight bars strung together in a row."

"Yes, rod bacilli," added Dr. Leslie, also looking. "Like long rows of hyphens, slender cylindric, non-motile chains joined end to end."

We looked at Craig inquiringly.

"Like that," he indicated, substituting another slide.

We looked again. The field had somewhat the appearance of an exaggerated war map with dark units of supposed troops.

"That's it," nodded Haynes.

Kennedy removed the slide. "Those are some anthrax germs I obtained here in the city from a pathologist," he said, turning a switch that threw on in a lamp a peculiar, purplish light. "This is a machine for the propagation of ultra-violet rays."

He placed the second slide, with its germs of anthrax, in the light, allowing it to play over the slide.

"Now look," he said.

We did. Something had evidently happened. The chains were broken and smaller units were moving.

"If anthrax germs are exposed for a few seconds, even, to ultra-violet light, they change more or less," Kennedy proceeded. "These new forms are not stable. They quickly change back again into their original form."

For about ten minutes we sat in silence while the weird light played as if with ghostly fingers on the deadly invisible peril on the little glass microscope slide.

"But if the action of the ultra-violet rays is continued," went on Craig, "the microbe changes into a coccus, and then into a filiform bacillus. This form is stable. And the germ is changed in other respects than mere shape. It has entirely new characteristics. It is a true mutation. It produces a disease entirely different from that of the anthrax bacillus from which it is derived. I have tried it on a guinea pig—and it has died in forty-eight hours."

Startled as I was by this remarkable discovery, I yet had time to watch Haynes. He had not taken his eyes off Kennedy once since he began to speak.

"In anthrax," continued Craig, "an autopsy reveals an enormous serous swelling, about the point of inoculation, with a large gathering of microbes which are formed in the blood and spleen. Death seems to be due to septic poisoning. But this new microbe—super-toxicus, I think it might well be named—produces no swelling and scarcely any microbes are to be found in the blood.

"The lungs are inflamed, with innumerable small abscesses. That is the internal form of the disease from breathing in the spores of these microbes. It has an external form, also, but that is by no means so deadly. One would say that death from the internal form of the disease was due to poisoning. The toxin of this microbe produces a sort of asphyxiation, cutting off and eating up the supply of oxygen.

"Such a condition is called cyanosis. That is why in Delaney it had the appearance of cyanogen poisoning. The effect was the same. But the trace of cyanogen in the air was merely a coincidence, Haynes. It wasn't cyanogen that killed. But it was something quite as deadly—and far harder to trace—a new germ!"

We listened, fascinated.

"A French scientist, a woman, Madame Victor Henri, a student at the Pasteur Institute in Paris, has shown that a new microbe can actually be created from anthrax germs by the use of ultra-violet rays. It is not like anthrax, but may be quite as deadly, perhaps more so.

"This discovery," he added earnestly, "proves for the first time that a living organism can be changed suddenly and artificially into an organism of a new and entirely different species. One can scarcely appreciate the importance of it. If the germs of different diseases can be transformed, the germ of one being changed into the germ of another, it will be a first step toward finding a way to change deadly germs into others that will be quite innocuous."

Kennedy paused impressively to let the horror of the thing impress itself on our minds. "But this criminal has been working for evil purposes in the wrong direction—creating a disease in order to cover up his tracks!"

One could almost feel the net closing.

"Delaney has fallen a victim to a new germ of which someone learned in Paris," Craig raced on, inexorably, "a germ that would never, in all probability, be discovered by American doctors, a germ that poisoned safely, surely, and swiftly by its deadly super-toxin."

A few moments before there had been a noise of a car outside the laboratory window, but in the excitement of Craig's startling revelation we had paid no attention.

A hasty tap at the door interrupted him. Before he could open it a very beautiful woman burst in, followed by a thick-set Irishman.

It was the Baroness Von Dorf and our friend Burke.

For a moment the two women fairly glared at each other.

"I've heard what Professor Kennedy just said," cried the Baroness, her eyes snapping fire. "Fortunately, I had to go to Washington and was able to protect myself by seeming to disappear. If I had stayed in New York another day, there is no telling what might have happened to me. Probably I should have got this disease internally instead of externally. As it was, I thought it would come near ruining my beauty."

Burke tossed a yellow slip of paper on the table near Kennedy. "That is something one of our special agents found and brought me today," he exclaimed.

Kennedy picked it up and read it, while Burke faced us.

The Secret Service man fixed his eyes on Madame Dupres. "As for you, my dear lady," he challenged, "how do you happen to be in New York with one of the greatest international crooks that ever troubled the police of five continents?"

"I—in New York?" she shrugged coolly. "Monte Carlo, Paris, Vienna, London—all were dead. I had to come here to make a living."

The Baroness drew herself up as if to speak.

"You scoundrel—you will give my apartment a bad name with your dirty cattle plague—will you!" ground out a voice harshly at my side.

I turned quickly. Ames had clutched Haynes by the throat. We were all on our feet in a moment, but there was no need of separating them. The veterinary was more than a match for the hot-headed little lawyer.

"Someone," shot out Kennedy, wheeling quickly, "figured that the cattle deal could be brought about quite naturally if Delaney were dead and the Baroness out of the way. Later he could reap the profit and carry off Madame Dupres into the bargain. And if anything were ever discovered, what more natural than to throw the suspicion on a veterinary who was supposed to know all about anthrax?"

Just then a half circle of nickled steel gleamed momentarily in Kennedy's hands. I recognized it as a pair of the new handcuffs that uncoiled automatically, gripping at a mere touch.

I saw it all in a flash, as I picked up the paper that Burke had tossed to Kennedy.

It was a telegram, and read:

A. A., The New Stratfield, Washington.

Return immediately. Coroner has Craig Kennedy on case.

D. D.

"It was a devilish scheme," snapped Kennedy, as the handcuffs circled the fake lawyer's wrists, "but it didn't work, Ames."