an exclamation of annoyance broke from nick carter’s lips.

“i didn’t give him credit for so much cunning,” he thought. “but hanged if i see why he should have felt it necessary to skulk away in that fashion. it can’t be possible that he suspects me, and i don’t know of any reason why crawford should not know of his going out.”

he concluded on the whole that it was probably an evidence of the instinctive slyness of the mentally affected, and nothing more. further, he concluded that stone had probably turned along the corridor in the other direction, used the servants’ stairs, and left by one of the side exits. of course, it was possible that his demented brain had urged him on to the use of the fire escape. the more he thought about it, the more he became convinced that the latter supposition was nearer the truth. it would be just like a man in stone’s condition to resort to such a ruse.

the miner’s disappearance had been a great disappointment to the detective. when he had discovered from the shadows on the drawn shade that stone was going out, his hopes had risen. he had counted on following the man and getting some line on his movements, but now that was out of the question.

he knew that it was useless to follow stone after that delay, but as a result of a few seconds’ deliberation, he decided not to let the chance slip altogether. donning his lightweight overcoat, and buttoning it up to his chin in order to conceal the conspicuous expanse of white shirt front—which might draw undesired attention—he softly raised the sash of his window and stepped out on the wide sill. the fire escape did not lead down directly past his room, but one end of the iron platform came within two or three feet of the window on the right side.

it was the simplest matter in the world for nick to grasp the rail and to hoist himself over.

the windows of the hotel were supplied with a novel patent catch which automatically fastened both the upper and lower sashes when the latter was pulled down. nick, therefore, took pains to leave his window open after passing through it.

it was this peculiarity of the windows which had brought him out on the fire escape. he knew that if stone had his wits about him, and had departed by that route, he must have left his window open or fixed it in some way to prevent his being locked out. it was to find if such precautions had been taken that he had made the effort.

when he approached stone’s window, the lower sash seemed to be closed, but a closer inspection revealed that a narrow wedge of wood had been inserted, leaving a half-inch crack at the bottom—just enough to permit a man’s fingers to get a purchase on the sash and raise it.

it was only a trivial thing, but it gave nick a clew to what was going to happen.

“he didn’t want the window to be locked by accident,” he mused, “and so he placed the wedge there. that means he’s going to come back this way, and it seems to me also that he wishes his partner to think he has been in all the evening—probably that he has gone to bed. it looks as if things were coming to a head.”

there was a cluster of small lights on a pole in the middle of the big courtyard, and the shades of many of the windows opening on it were up. it was light enough, therefore, for the detective to see with reasonable clearness—and to be seen, if any one happened to look in his direction.

he leaned over the rail and peered down. he was only at the level of the second floor, but the pavement of the courtyard was flush with the basement; therefore, two floors beneath him. he looked to see if the lowest ladder of the fire escape was in place but saw that it was not.

“stone probably dropped from the last platform,” he concluded. “it wouldn’t have been anything for a man of his active habits. i wonder how he expects to get back, though. by george! there’s a painter’s ladder lying on the pavement on the other side of the court. such things never ought to be left around. the sight of that ladder would tickle a thief to death. stone probably saw it and made his plans accordingly.

“he expects to use it to reach the lower platform, but i’m curious to know what else is in his mind. according to crawford he’s sane enough in all respects but one—and he wasn’t born yesterday. he must know that he can’t leave the ladder set up against the landing when he comes back to his room. if he does, there will surely be an investigation in the morning, if not before. does he merely think that there will be a little burglar scare which won’t affect him, or is there something deeper in all this?

“has he gone off half-cocked, or—— great ned! i wonder if that can be it. if he were going to bring some one back with him—some one who would be leaving by the same route later on who could put the ladder back where it was originally—that would effectually remove the difficulty. if stone is as shrewd as i give him credit for being, i’ll wager that’s what’s in the wind. and i can give a guess at his prospective visitor’s identity.”

he referred, of course, to doctor follansbee; and the possibility that the latter was expected later on that night was enough to stir his pulses. it suggested that the period of inactivity was about to come to an end, and that the test of his unsolicited guardianship of winthrop crawford was at hand.

stone had gone, and it was unnecessary, as well as useless, to attempt to follow him. all that remained was to await his return as patiently as possible, and in the meantime to keep an eye—or at least, an ear—out for crawford.

the latter proved an easy matter, for about an hour later he heard the door of crawford’s room open and close, and from his window saw the light flash up in his new friend’s.

a glance at his watch told him that it was now almost ten o’clock. he knew that crawford was a man who rose early, and there was every probability that the miner was about to turn in for the night.

nick’s own room had remained in darkness. he now drew a chair close to his window and took up his vigil, his arms resting on the sill. fifteen or twenty minutes later the light vanished in crawford’s room. in order to make sure, the detective hurriedly rose, slipped to his own door, and opened it slightly. his friend did not appear in the corridor, which was sufficient proof that he was going to bed.

nick reclosed his door and locked it. “you are settled for the night,” he thought; “and now for stone.”

he was possessed of the infinite patience that means so much to a detective, and is so essential to the success of any one who takes up that profession. the rumble of traffic gradually died down, and light after light went out in the hotel. at last, in the distance the clock in the metropolitan tower struck twelve. yet the bunch light still glowed in the courtyard below, and many windows were rectangles of light, bright or subdued, as the case might be, for new york is very slow to go to bed.

the detective’s lower sash was raised about six or eight inches, and that fact at length enabled him to hear a slight sound in the courtyard, even before his watchful eyes had warned him of the approach. he did not make the mistake of leaning out of the window. indeed, it would not have been easy to do so, in view of the narrow space he had left.

in any case, it was unnecessary. the painter’s ladder was well within his range of vision, and a few moments later he had the satisfaction of seeing two figures steal into view and grasp it. they had come from the open end of the courtyard, which was on nick’s side, and out of his sight.

they picked up the ladder and started to sidle across the court in the direction of the fire escape. there was more than a hint of sinister purpose in their furtive movements, and an instant later first one and then the other raised his head and scanned the tiers of windows above, as if to make sure that they were not observed.

as they did so, the lights of the cluster fell on their faces for a fleeting instant, and the muscles of nick’s jaws tightened. he had barely glanced at the taller figure. it was the shorter, slightly stooped one which interested him most, and he had seen all that was necessary.

the second man wore the repellent mask of stephen follansbee.