The trail picked up by Patsy Garvan was becoming so hot, indeed, as he had expressed it, that he now had absolutely no idea of quitting it. He followed the two suspects through Prince Street, noting that they were engaged in a subdued and very earnest discussion, with Shannon doing most of the talking, but Patsy did not venture to attempt overhearing them.

“I could pick up only a word or two at the most, and must take a chance of being seen and suspected,” he rightly reasoned. “That would put them on their guard and knock a further espionage on the head. I’d better keep them in the dark and try to see what’s coming off. If Shannon brought orders from some one to this sinister-looking scamp, it’s long odds that Doctor Devoll was the one. There sure is something in the wind.”

It soon was evident to him that the two men were heading for the stable in which Toby Monk kept his car, and he began to fear that he was booked for the same difficulties he had had the previous night. He felt quite sure of it, in fact, when both men entered the stable and Toby Monk partly closed the front door, precluding a view from the street.

Presently, however, a feeble light from a smoky lantern could be seen, and Patsy muttered perplexedly:

“What do they want of that? They can’t be going out with the car, after all, or a lantern would not be needed. They may have come here only to escape observation while planning a job. I can very soon find out by making use of the back window again.”

He was on his way with the last thought. A couple of minutes brought him to the back fence, over which he climbed noiselessly, and then crept near enough to see and hear through the dusty back window.

Toby Monk was on his knees with a box of blue paste and a brush, engaged in altering the figures on the rear number plate of the touring car.

Shannon was seated on a box near by, with his brawny arms resting on his knees, while he grimly watched the chauffeur’s artistic alterations.

“You’d better let the top down, too, Toby,” he advised, after a moment. “That will help.”

“Mebbe so, Jim, since I’m never seen with it down,” Monk replied. “I’ll drop it before leaving.”

“Besides, it might be a bit in the way,” Shannon pointedly added. “It’s easier to get into an open car. This trick has got to be turned on the jump, mind you.”

“I know that, Jim, all right, and you can bet I’ll do my part.”

“Have I made it perfectly plain to you?”

“As plain as twice two.”

“The signal——”

“There’s no need to repeat it, Jim,” Toby protested, interrupting, much to Patsy’s disappointment. “I’ve got the whole business down pat, so far as my part in the job goes. You may tell his nibs he may bank on that.”

“The hour——”

“I know,” Monk again cut in impatiently. “You need never repeat an order that he sends me. There’s too much coming, Jim, for me to go lame.”

“I’ll be off, then, Toby, and tell him I found you,” said Shannon, rising abruptly. “He’ll be waiting for me by this time.”

“Go ahead, then, and I’ll see you later.”

“Sure thing, Toby, bar a slip-up of some kind,” Shannon paused to add. “You know what we are up against.”

“Rats! Trust his nibs to get the best of that bunch. No dicks can fool him. He’ll put something over on them that they never heard of.”

Shannon laughed grimly, picking his way around the touring car, and left the dingy, dimly lighted stable.

Patsy Garvan hesitated only for a moment. He remembered the previous night. He knew that he might find it utterly impossible to follow Toby Monk, who evidently was soon going to use his car, and Patsy immediately stole around the stable, taking advantage of the darkness to dart back of the rear dwelling, and in another moment he was stealthily following Shannon up the street.

“Going to tell his nibs, is he?” thought Patsy, with ever-increasing elation. “If I don’t learn who is back of this whole business, then there’ll be something wrong with the cards. Get the best of the chief, will he? I guess not!”

He found it easy to shadow his unsuspecting quarry. He trailed him to an outskirt of the business section, where Shannon paused briefly in a gloomy doorway and put on a disguise. Five minutes later, after looking sharply in each direction, he entered a court flanking one end of a large stone building.

“By gracious!” thought Patsy, gazing up at it. “This is the Waldmere Chambers, the building in which Todd was killed. Has the gang a headquarters here, or is it where only the chief himself hangs out? In either case, by Jove! I’m getting in right at last.”

Stealing nearer, he peered cautiously into the court. Shannon had disappeared in the deeper darkness. Following noiselessly, Patsy brought up at a solid wooden gate about six feet high, and he then heard a door closed and the snap of a lock. It told him plainly enough that Doctor David Devoll’s burly attendant had entered the building.

“Gee whiz! I must not lose track of him,” Patsy muttered under his breath. “I’ll take chances to guard against that. Locked, by thunder!”

Patsy had vainly tried to open the gate. He saw that it closed an alley about five feet wide between the rear of the Waldmere Chambers and the blank back wall of another lofty building. He drew himself up and looked over it. He could see a door some ten feet away, and directly above it a single-lighted window, the roller shade of which was drawn nearly to the sill.

“That’s a rear office on the second floor,” Patsy rightly reasoned. “That door must open into a basement, however, for the land slopes toward the front of the building. By Jove! I must find out what’s doing.”

Without a sound that could have been heard in the office mentioned, he climbed over the gate and dropped upon the pavement in the alley, then picked his way through the gloom toward the door. He then found that it was an ordinary storm door, opening outward and protecting an interior one, which was securely locked.

He listened vainly for any sound from within, also at two ground-glass windows near by, evidently those of a basement, then as dark as a pocket. Both were securely fastened.

“Gee! I’m no better off,” he said to himself. “If I could get up to that lighted window, I might learn whether Shannon is there, or—by gum! I have it. I can both see and hear, all right, by standing on the top of this outer door. It’s some stunt to get up there, though, without being heard.”

He demurred only briefly, seeing no other way to accomplish his object. He opened the door, then hung by his hands from the top for a moment, finding that the hinges would support him. He then drew himself up, working one leg over the outer corner, and finally worming himself to a seat on the unsteady perch. Twice he had swung against the building, but met the wall noiselessly with his shoulder.

Reaching up, he then could grasp the stone sill of the lighted window. He drew himself up, hanging clear of the door, then nearly closed it with his feet, bringing it to a position directly under the window, enabling him to stand in a crouching posture on it, still grasping the stone sill.

A beam of light from under the roller shade then fell on Patsy’s grimly determined face. Voices from within reached his ears. He peered into the room and saw, seated in opposite chairs, Jim Shannon and Professor Karl Graff.

“The man I trailed to Leary’s road house! The man who killed the cat!” The thoughts flashed swiftly through Patsy’s mind. “By gracious, it now is a cinch! He’s the big finger of the gang. But who the deuce is he?”

Though puzzled as to his identity, Patsy read plainly in Professor Graff’s gray-bearded face that he was discussing something of serious importance. His narrow eyes had a vicious gleam and glitter. He was drawn forward in his chair, with his hands clenched on his knees and his gaze riveted on Shannon’s dark face, from which he had removed his disguise.

“You made it clear to him, Jim, perfectly clear?” Graff was asking. “There must be no mistake, no delay.”

“There’ll be none,” Shannon gruffly informed him. “You can bank on that.”

“The number plates——”

“I left him changing them.”

“The position he is to take with the car——”

“He knows the very spot.”

“The signal——”

“Your flash light—he knows,” Shannon cut in again. “He’ll be watching for it.”

“And what he then must do?”

“The whole business. He has it down pat from A to Z.”

Graff settled back in his chair. He appeared satisfied with these forcible assurances. He fell to rubbing his hands, his eyes gleaming with malicious triumph, a gleam and glitter so intense that Patsy Garvan felt that he was gazing at a madman.

“If he isn’t dippy, a pronounced victim of criminal mania, I’m no judge of human faces,” he said to himself. “Human be hanged! He has the look of a devil, and all the makings of one, if I’m not mistaken.”

“We’ll balk him, thwart him, turn this trick on him, Shannon, in spite of all he can do,” Graff snapped viciously after a moment. “Then, if he dares to remain in Madison—well, God help him! His fate will be on his own head. I have told him. I have warned him.”

“He means the chief,” thought Patsy. “This was the rascal who sent him the letter, and he refers to the theft of Mrs. Thurlow’s pearls. They’ve been planning it, and that’s the job Toby Monk is booked for to-night. If I can but learn the details of their scheme, it will be soft walking for the chief to foil their game and collar the entire gang. I’m on the way, all right.”

Patsy felt reasonably sure of it, indeed, and he was missing nothing that passed between the two conspirators. Shannon appeared oblivious to Graff’s display of feeling, though he smiled a bit grimly and said:

“You can turn the dick down, all right, if need be, and none would get wise. All I hope is that he won’t be able to queer this job. There would be something coming to us from it, a deal more than usual.”

“It’s as sure as if you already had it in your pocket, Shannon, if my instructions are carefully followed.”

“They will be,” Shannon nodded. “What does Tim Hurst think about it? Where does he fit in?”

“He’s to work the trick with me.”

“Any one else?”

“Only Dorson.”

“Is it safe to rely upon him?”

“There will be no safety for him if he disappoints me,” Graff declared, with vicious asperity. “He knows what it will cost and that he’ll pay the price. You know what befell the one treacherous cur who dared to defy me and threatened to expose——”

“Enough of that,” Shannon cut in, with a growl. “I don’t like to think of it, much less talk about it. What has become of Hurst, anyway?”

“I have not seen him since last night, after he searched the rooms of that servile cur.” Graff spoke with an ugly snarl. “He found papers that would have exposed us, but they now are ashes only. Luckily, too, he was in time to down one of the Nick Carter gang, who otherwise would have found the same and had us by the ears.”

“We’ll get you all right, sooner or later,” thought Patsy. “Tim Hurst, eh? The masked man whom Chick encountered. Give us a little more time and we’ll uncover all of these hidden faces.”

“Downed him, did he?” queried Shannon. “He must be a lightweight dick that Tim could down, for all he’s quick and clever.”

Professor Graff laughed for a moment as if much tickled, but his mirth had qualities that sent a chill down Patsy’s spine.

“I had made it easy for him,” Graff replied, still chuckling with evil pride. “He wore an unsuspected weapon, an electrical device of mine that would overcome a horse. Let Tim alone to make good when in a tight place.”

“But it’s near seven,” Shannon growled, glancing at the clock. “If he’s to work with you to-night——”

“He’ll come,” Graff cut in quickly. “He’ll show up on time. He’s due here now.”

“Due here! Will he sneak in this way, or enter from the front street? If he comes while I’m up here——”

Patsy caught his breath, scenting speedy trouble.

A key had been thrust into the lock, and almost instantly the gate was opened and hurriedly closed. A slender, black-clad figure had entered the alley, a thin-featured, keen-eyed man of about thirty, who quickly jerked the key from the lock.

Patsy had as quickly decided what he would do. He knew he could not leap down from his unsteady perch undetected and retreat farther into the alley. He took, therefore, his only chance to escape observation, knowing that he could not hold up the intruder without alarming his confederates. Firmly grasping the stone sill of the window, he drew up his legs and raised his feet from the top of the door, hoping the man would pass under him and enter without seeing him.

The ruse came near proving successful. Tim Hurst strode quickly to the storm door and flung it open, then fished out a key to the inner one. He had heard nothing alarming nor seen the crimped figure hanging close to the dark wall directly above him.

Just then, however, a bit of cement broke from the stone under Patsy’s rigid grasp, and it fell straight down upon Hurst’s head. He drew back as if electrified, looking up, and as quick as a flash he guessed the truth. On the instant, too, while he uttered a short, sharp whistle, he leaped up and seized Patsy’s legs, snarling fiercely:

“Come down here! Let go, blast you, or——”

Hurst was not given time to say more.

Patsy heard Graff and Shannon spring up and rush down a back stairway in response to the whistle, and he realized that only quick work could save him. He let go of the sill and dropped straight down upon Hurst’s head and shoulders, worming quickly around as he pitched over him, and trying to grapple him around his arms and waist.

The lithe and wiry rascal was alert, however, and as quick of motion as a cat. He also twisted around when Patsy fell, spreading his feet to steady himself, and then, with a lightninglike lurch toward the building, he brought Patsy’s head against the stone wall, a blow that nearly cracked his skull and dazed him so that he hardly knew what immediately followed.

In a vague way, however, he realized that he was being roughly handled, that Graff and Shannon had rushed out into the alley, and that the three men were hurriedly taking him into the building.

He heard both doors closed and locked, then was conscious of being placed roughly on a cold cement floor, with two of the ruffians nearly crushing him in the inky darkness. This was dispelled in a moment by a glare of electric light, and the cobwebs then had cleared from his brain sufficiently for him to size up the surroundings.

He saw at a glance that he was in a chemical laboratory, a large, square room with shelved walls, laden with bottles, jars, carboys, and the like. A zinc-covered table was littered with the customary articles required by a chemist. There was a closet in one corner. Near by was an open door, an adjoining entry, and a narrow stairway leading up to the room in which the two men had been seated.

Patsy still was gazing around when Graft approached him, commanding his two confederates to bind him, which they quickly proceeded to do with cords brought from the closet, while Tim Hurst hurriedly stated where he discovered their captive.

“Who are you? Who sent you here to play the spy?” he fiercely questioned.

Though he keenly realized that he was in wrong, and that much of his good work might prove futile, Patsy lost neither his head nor his nerve.

“No one sent me,” he answered curtly. “I came on my own hook.”

“You lie!” Graff snapped harshly. “You are in Nick Carter’s employ.”

“By Heaven, I guess that’s right,” Shannon agreed, with a snarl. “He’s one of the dicks.”

“We’ll dick him! We’ll dick him all right when the time comes,” Graff fiercely declared. “But not now, not yet. The Thurlow pearls are of first importance, and I have only time to prepare for that job. We’ll settle with him later. Gag him, Shannon, and lock him in the closet. You must wait here and watch till we return. Make sure the whelp can’t escape. I’ll fix him later. I’ll fix him.”

“Gee whiz!” thought Patsy. “If he makes good as he looks, I can see my finish.”