“Yes, my friend, I intend to earn my fee,” the cold voice declared to the empty room. “The only difference is that the fee is somewhat larger than I’ve given you reason to believe.”  
Leaning back in his chair, Doctor Stephen Follansbee blotted the check, then, taking a bunch of keys from his pocket, he unlocked the top drawer of the desk and slipped the check into a small leather-bound book which lay inside.
 
“Just to make sure that I receive my just dues,” he went on, “I’ll turn this check in on Saturday instead of Monday. You’re mad enough on one point, James Stone, but you’re a shrewd man outside of that, and it might occur to you to stop payment on that check.” His short, cackling laugh rang put anew.
 
Half an hour later he left his house. He did not seem to be in as much of a hurry as he had said, as he made his way leisurely, and on foot, to his destination.
 
He made a striking figure as he proceeded. His face alone would have attracted attention anywhere, but his dress was eccentric in its shabbiness. His arms were folded behind his back in a very unusual, but thoroughly characteristic way, and his little, lashless eyes were bent on the ground. Many passers-by stopped to stare at him as he passed, and not a few recognized him.
 
“He’s the great Doctor Follansbee, the head of St. Swithin’s Hospital!” they told one another. “You’d never think it to look at him, would you? He looks more like a mummy than anything else.”
 
Careless of these comments and of the mild sensation his appearance always created, Follansbee soon reached the hospital, passed through the imposing entrance, and went on down the broad corridor to his private room. As soon as he had seated himself at his desk and glanced hastily through the few reports and other documents which lay there, he pressed one of several buzzer buttons on a small switchboard attached to his desk.
 
In response to the summons, the resident physician in charge quickly entered. Follansbee spent half an hour listening to the reports of the various cases and to matters of hospital routine. That done, he issued a few instructions in his sharp voice, and the physician left the room.
 
Other heads of departments followed, and for two hours Follansbee was constantly engaged. At the end of that time, though, he rose to his feet and passed through into an adjoining room which was fitted up as a private laboratory and workshop.
 
Crossing to one side of the room along which rows of shelves had been placed, he opened a small, glass-doored cupboard, and, leaning forward, took a small case of test tubes from one of the shelves, which contained serum of various types. Going back to his desk, the doctor seated himself and began to work. Evidently he was thinking something out with the aid of pencil and paper. He had a pad in front of him, and on it he scrawled a few lines of straggling writing. Then, after a prolonged pause, he jotted down a few more words.
 
“Yes,” he said to himself presently, “I think that will be the best way. There’s no reason why Crawford could not have been exposed to disease before his arrival. He has just landed in New York, and if I succeed in getting at him within the next day or so, there will be no reason for any one to suspect.”
 
He leaned back in his chair.
 
“I’m sorry, though, that that mad fool attacked him,” he went on musingly, “for, despite what Stone says, I feel sure that Crawford must be on his guard now.”
 
That was the point in the case which baffled Follansbee for the moment. He could not understand why Crawford, after no less than three attempts had been made on his life, should still be willing to occupy a room which connected directly with that of his would-be murderer. At last, with a shrug of his shoulders, he dismissed the subject.
 
“After all, it doesn’t matter very much,” he mumbled to himself. “The attempts which Stone has made are only known to four or five persons at most. They are the two most concerned, young Floyd, and the stranger who, according to Stone’s admission, separated him and Crawford on the boat. His knowledge and that of Floyd would be dangerous if Crawford were to be put out of the way in any ordinary fashion, but neither would be suspicious if he succumbed to a tropical disease. It would never occur to them to question his death under such circumstances, and even if it did, they wouldn’t give Stone credit for so much ingenuity. As for me, I’m above suspicion, except in the eyes of a very few persons—notably Nick Carter’s. I shouldn’t like him to get wind of this, but there’s little or no likelihood of his doing so.”
 
James Stone had not known of th............