Craig read quickly and I followed him, fascinated by the letter from its very opening paragraph.

"Dear Madam," it began. "Having received my diploma as doctor of medicine and bacteriology at Heidelberg in 1909, I came to the United States to study a most serious disease which is prevalent in several of the western mountain states."

So far, I reflected, it looked like an ordinary appeal for aid. The next words, however, were queer: "I have four hundred persons of wealth on my list. Your name was--"

Kennedy turned the page. On the next leaf of the letter sheet was pasted a strip of gelatine. The first page had adhered slightly to the gelatine.

"Chosen by fate," went on the sentence ominously.

"By opening this letter," I read, "you have liberated millions of the virulent bacteria of this disease. Without a doubt you are infected by this time, for no human body is impervious to them, and up to the present only one in one hundred has fully recovered after going through all its stages."

I gasped. The gelatine had evidently been arranged so that when the two sheets were pulled apart, the germs would be thrown into the air about the person opening the letter. It was a very ingenious device.

The letter continued, "I am happy to say, however, that I have a prophylactic which will destroy any number of these germs if used up to the ninth day. It is necessary only that you should place five thousand dollars in an envelope and leave it for me to be called for at the desk of the Prince Henry Hotel. When the messenger delivers the money to me, the prophylactic will be sent immediately.

"First of all, take a match and burn this letter to avoid spreading the disease. Then change your clothes and burn the old ones. Enclosed you will find in a germ-proof envelope an exact copy of this letter. The room should then be thoroughly fumigated. Do not come into close contact with anyone near and dear to you until you have used the prophylactic. Tell no one. In case you do, the prophylactic will not be sent under any circ.u.mstances. Very truly yours, DR. HANS HOPF."

"Blackmail!" exclaimed Kennedy, looking intently again at the gelatine on the second page, as I involuntarily backed away and held my breath.

"Yes, I know," responded Mrs. Blake anxiously, "but is it true?"

There could be no doubt from the tone of her voice that she more than half believed that it was true.

"I cannot say--yet," replied Craig, still cautiously scanning the apparently innocent piece of gelatine on the original letter which Mrs.

Blake had not destroyed. "I shall have to keep it and examine it."

On the gelatine I could see a dark ma.s.s which evidently was supposed to contain the germs.

"I opened the letter here in this room," she went on. "At first I thought nothing of it. But this morning, when Buster, my prize Pekinese, who had been with me, sitting on my lap at the time, and closer to the letter even than I was, when Buster was taken suddenly ill, I--well, I began to worry."

She finished with a little nervous laugh, as people will to hide their real feelings.

"I should like to see the dog," remarked Kennedy simply.

"Miss Sears," asked her mistress, "will you get Buster, please?"

The nurse left the room. No longer was there the laughing look on her face. This was serious business.

A few minutes later she reappeared, carrying gingerly a small dog basket. Mrs. Blake lifted the lid. Inside was a beautiful little "Peke," and it was easy to see that Buster was indeed ill.

"Who is your doctor?" asked Craig, considering.

"Dr. Rae Wilson, a very well-known woman physician."

Kennedy nodded recognition of the name. "What does she say?" he asked, observing the dog narrowly.

"We haven't told anyone, outside, of it yet," replied Mrs. Blake. "In fact until Buster fell sick, I thought it was a hoax."

"You haven't told anyone?"

"Only Reginald and my daughter Betty. Betty is frantic--not with fear for herself, but with fear for me. No one can rea.s.sure her. In fact it was as much for her sake as anyone's that I sent for you. Reginald has tried to trace the thing down himself, but has not succeeded."

She paused. The door opened and Reginald Blake entered. He was a young fellow, self confident and no doubt very efficient at the new dances, though scarcely fitted to rub elbows with a cold world which, outside of his own immediate circle, knew not the name of Blake. He stood for a moment regarding us through the smoke of his cigarette.

"Tell me just what you have done," asked Kennedy of him as his mother introduced him, although he had done the talking for her over the telephone.

"Done?" he drawled. "Why, as soon as mother told me of the letter, I left an envelope up at the Prince Henry, as it directed."

"With the money?" put in Craig quickly.

"Oh, no--just as a decoy."

"Yes. What happened?"

"Well, I waited around a long time. It was far along in the day when a woman appeared at the desk. I had instructed the clerk to be on the watch for anyone who asked for mail addressed to a Dr. Hopf. The clerk slammed the register. That was the signal. I moved up closer."

"What did she look like?" asked Kennedy keenly.

"I couldn't see her face. But she was beautifully dressed, with a long light flowing linen duster, a veil that hid her features and on her hands and arms a long pair of motoring doeskin gloves. By George, she was a winner--in general looks, though. Well, something about the clerk, I suppose, must have aroused her suspicions. For, a moment later, she was gone in the crowd. Evidently she had thought of the danger and had picked out a time when the lobby would be full and everybody busy. But she did not leave by the front entrance through which she entered. I concluded that she must have left by one of the side street carriage doors."

"And she got away?"

"Yes. I found that she asked one of the boys at the door to crank up a car standing at the curb. She slid into the seat, and was off in a minute."

Kennedy said nothing. But I knew that he was making a mighty effort to restrain comment on the bungling amateur detective work of the son of our client.

Reginald saw the look on his face. "Still," he hastened, "I got the number of the car. It was 200859 New York."

"You have looked it up?" queried Kennedy quickly.

"I didn't need to do it. A few minutes later Dr. Rae Wilson herself came out--storming like mad. Her car had been stolen at the very door of the hotel by this woman with the innocent aid of the hotel employees."

Kennedy was evidently keenly interested. The mention of the stolen car had apparently at once suggested an idea to him.

"Mrs. Blake," he said, as he rose to go, "I shall take this letter with me. Will you see that Buster is sent up to my laboratory immediately?"

She nodded. It was evident that Buster was a great pet with her and that it was with difficulty she kept from smoothing his silky coat.

"You--you won't hurt Buster?" she pleaded.

"No. Trust me. More than that, if there is any possible way of untangling this mystery, I shall do it."

Mrs. Blake looked rather than spoke her thanks. As we went downstairs, accompanied by Miss Sears, we could see in the music room a very interesting couple, chatting earnestly over the piano.

Betty Blake, a slip of a girl in her first season, was dividing her attention between her visitor and the door by which we were pa.s.sing.

She rose as she heard us, leaving the young man standing alone at the piano. He was of an age perhaps a year or two older than Reginald Blake. It was evident that, whatever Miss Betty might think, he had eyes for no one else but the pretty debutante. He even seemed to be regarding Kennedy sullenly, as if he were a possible rival.