“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 the detective’s identity, because the latter’s name had not appeared on the passenger list of the cortez, and, strictly speaking, it had been a breach of confidence on the part of the chief steward when the latter had revealed carter’s name to crawford. had follansbee known more of the mysterious stranger whose intervention had been so unfortunate from stone’s standpoint, even his cold, hard calm would have been broken up, and he would have cut off his right hand rather than have anything to do with the affair. so far as his knowledge went, however, it seemed sufficiently safe to venture on what he had in view.

“anyhow, i run no risk,” he concluded. “both stone and crawford seem to have no friends in the city, and if there should be a coroner’s inquest the death would be put down as resulting from natural causes.”

he ran his fingers over the test tubes with a touch that was almost caressing, and on his sallow, leathery face there rested a malevolent smile.

“my first step in the career of crime,” he resumed, “was not very successful, i’ll have to admit. it involved considerable risk, and i was infernally lucky to have crawled out of it as well as i did. i was a fool then, though, and i won’t take any such risks in future. i’ll be the ‘man behind’ this time. stone will execute the work, and when it’s duly accomplished, the reward will be mine, and i think i can worry along for some time on that amount.”

floyd, in his misguided effort to be thorough, had sent a number of details which might well have been omitted. they had enabled follansbee to make a great show of knowledge, and by his evasions in respect to the source of it had greatly contributed to stone’s bewilderment. they had also made it possible for the unscrupulous head of st. swithin’s to fill in the check for the amount that was only fifty thousand dollars short of the entire sum which stone was supposed to have realized from the sale of the condor mine. he would have liked to claim even more, but he did not dare, for fear of overdrawing the miner’s account and thereby creating a difficulty when the time came for the bank to honor the check. therefore he had shrewdly fixed his “fee” at that sum, in order to allow for any reasonable withdrawals on stone’s part.

in that and other ways floyd’s letter had been of the greatest assistance, and had served a purpose the nature of which its writer had never dreamed. it would have seemed incredible to the young physician, whose profession was sacred to him, and in whose eyes stephen follansbee was everything that was desirable—except in external appearances.

well he might. few would have been willing to believe for a moment that the famous specialist could be guilty of such juggling with checks, and much less that he would consent to engage in a criminal conspiracy, the end of which was scientific murder, with any man—least of all one he knew to be mentally diseased. yet, such was the fact.

now and then a physician—sometimes a really great one—goes wrong and plays false to the tremendous responsibility which he has assumed. stephen follansbee was one of the most conspicuous examples of this. he had started out with the highest motives, and worked his way up by hard work and sheer weight of ability. he had always been supremely selfish, however, and had possessed little or no heart. he had won fame in spite of his repellent appearance and his cold, unsympathetic nature. but that fame, and the reward which followed it, had not been enough for him. there was an evil streak in him, and it had become more pronounced as the years passed.

he had begun by using his position to cover up indefensible experiments on patients, especially those who were poor and obscure. emboldened by his freedom from penalty, he had gone on and indulged in more daring and ruthless work. most of it had been in the name of medical knowledge, to be sure, and had had the sanction of not a few fellow practitioners, but it was none the less criminal.

at length, a year or so before, he had dared to try a particularly heartless experiment on a famous author, but while it was still in one of its early stages, nick carter had learned of it—it doesn’t matter how—and had effectually interfered. incidentally, the detective had prevented follansbee from collecting fifty thousand dollars for his services, as he called them.

it had not been an indictable offense, and so follansbee went unpunished. carter had been obliged to content himself with a scathing denunciation, and a warning to keep straight in the future. to the best of the detective’s knowledge, follansbee had done so. this chance, however, had been too much for the distinguished scoundrel.