Harry made good his promise. For once fate seemed with him. A huge job lot of books, which it had taken him three days to bring from the stock-room to the first floor, was to be placed on sale in the department and the handling of this stock kept him busy on the floor, where he could see what went on.

The day before the sale he was detailed to work after the store had closed. The majority of the men in 85 had also been detained for night work and among them was Mr. Farley, the sleepy-eyed salesman.

A week had passed since Harry’s conversation with Miss Welch. During that time the boy had watched Mr. Farley whenever he had the opportunity to do so, without being observed. His vigilance had met with no reward. To all intents the salesman appeared to be perfectly open and above-board in his dealings. Harry felt almost ashamed of himself for shadowing a man of whom he had really no cause for suspicion other than the fact that he had charge of the sets and that Miss Welch had suggested that he might bear watching. Even though there were a chain of thieves among Martin Brothers’ employees, it might not extend to the book department. Still the conversation he had overheard pointed plainly to the dishonesty of someone in Department 85.

Late that afternoon, however, Harry chanced to witness something which bore out Miss Welch’s suggestion. The boy was hard at work, arranging a table of bargain books when the sound of voices in his ears caused him to glance up. Mr. Farley stood before a shelf of special books devoted to arts and crafts. It was situated directly across the narrow aisle in which Harry was working. The man’s back was toward the boy. Beside him stood a pretty young woman. She was talking animatedly on the subject of interior decorating and examining with interest the various books the salesman showed her.

“How much is this book?” Harry heard her ask.

“Five dollars,” was the salesman’s response.

The young woman turned the leaves of the book as though undecided whether she wished to pay that price for it. The salesman watched her narrowly.

“I’ll take it,” she said at last, “but need I have it wrapped? I wish to make a train and I can save time by tucking it in this bag.” She pointed to a leather traveling bag she had set down on the shelf. Fumbling in her hand-bag she took from it a five-dollar note and handed it to Mr. Farley.

“That will be all right, madam,” Harry heard him say. He glanced cautiously up and down the aisle, still with his back toward Harry. The woman hastily opened her traveling bag, dropped the book into it and hurried out of the department. The man watched her out of sight, then he strolled off in the opposite direction without looking back, but as he went, Harry’s watchful eyes saw him thrust the hand that held the money into his trousers pocket. When he withdrew his hand it was empty.

“He’s going to keep that money,” sprang to Harry’s mind, then, anxious to give the man the benefit of the doubt, “Perhaps he has put it in his pocket until he gets his sales book.” The boy strolled slowly behind the salesman, determined to see what Mr. Farley intended to do with the money. It soon became evident that the man was not searching for his book on which to record the sale. He walked to the end of the aisle, then crossed over to the other side of the department. Harry dodged behind a high pile of large dictionaries that had been stacked at the end of the aisle. From this point of vantage he watched Mr. Farley for at least ten minutes. During that time the man made no effort to record the sale. Instead, he approached one of the saleswomen and entered into a conversation with her. Spying a customer who was examining a set of Thackeray, he made his way to his own stock, with Martin Brothers’ money still reposing in his trousers pocket.

Here Harry’s watch ended. He could spend no further time shadowing the man. He went slowly back to the table on which he had been at work, hardly knowing what to do. He had seen Mr. Farley pocket the money, but how could he prove what he had seen, were he to accuse the man openly? He had no way of finding out who the customer was, or where she lived. If Mr. Farley were confronted with Harry’s story he would no doubt deny the whole transaction, or make some sort of clever explanation that would entirely discount Harry’s accusation.

“I’ll tell Miss Welch,” decided the boy. He made his way to the exchange desk, but his friend was too busily engaged with a row of more or less patient women, afflicted with the exchange habit, for confidences.

“I’ll tell her as soon as she isn’t so busy,” he decided. Before that time arrived he was sent up to the stock-room for a small consignment of books for which a saleswoman had an order on the following morning. When he returned to the floor the second closing gong had rung and Miss Welch’s desk was deserted.

“I suppose I’d better go and eat my supper.” Harry turned in disappointment from the exchange desk and went downstairs to the basement, pondering what he had best do. As is the custom in large department stores, the employees who work after the store’s regular hour for closing receive their supper at the management’s expense. They are usually given from thirty to fifty cents and allowed time enough to go to an outside restaurant for their evening meal. Certain stores, however, make it a point to serve supper to their salespersons working overtime. Martin Brothers were among the latter, and served their night workers with a substantial meal in the basement restaurant.

Harry had just begun his supper when he saw Mr. Farley enter the restaurant in company with a slender young man whose black eyes and hair, together with a small black moustache, gave him a decidedly foreign air. The two seated themselves at a table some distance from Harry, and with their heads close together began what appeared to be an extremely confidential conversation. He noted that when the waiter came to take their order they stopped talking and waited until he was well out of hearing before resuming their confab.

“I wonder who that man is,” was Harry’s thought. “I don’t believe I ever saw him before.” As he sat watching the two salesmen, Fred Alden, the other stock boy for Department 85, slid into the chair opposite Harry.

“Any objections to the pleasure of my company for supper?” he grinned cheerfully. He was a tow-headed, homely youth, older by two years than Harry, and his unfailing good humor was proverbial in the department.

“I’m glad to have you. I hate to eat alone. I’d have waited for you to go to supper, but I wished to see Miss Welch. She’d gone home, though, so I came on down stairs,” explained Harry. Seized with a sudden idea he asked carelessly, “Who is that man with Mr. Farley? They’re over there.” Harry indicated them with a nod of his head.

“Who’s he? Oh, he’s a salesman in the upholstery. He’s a Frenchman, and thinks he’s a whole lot. He talks like an American, though. Sometimes when he gets mad or excited you can tell he’s a foreigner. The messenger kids used to tease him to see him get wrathy. He’s got an awful temper.”

Harry’s heart gave a sudden leap. The unfamiliar voice he had heard that morning of some weeks past had held a curious note which he knew to be out of the ordinary, yet was at a loss to guess why. Now it was all clear. The peculiarly accented words were the speech of an alien. At last he was on the trail of at least two thieves. Whether that trail led out of the book department and through the store, he could not know. He only knew that Miss Welch’s random suspicion had hit the mark.

During the remainder of the meal he let Fred carry on the greater part of the conversation, a proceeding which exactly suited the other boy, who was a chronic talker. Harry’s thoughts were busy with his discovery. He could not be sure of his man until he heard the dark young man speak. But while he pondered as to his next move he saw Mr. Farley and his companion rise from the table. Harry sprang to his feet, leaving his dessert half eaten. “I’m sorry I can’t wait for you, Fred,” he apologized, “but I—I—must go.” Without further words he hastened toward the stairs.

The two men were half way up the stairs when Harry set foot on the first step. Up he sped, so quietly that they did not hear him. At least, they did not turn around. He was only three steps behind them as they reached the first floor. To his intense chagrin they stopped short at the head of the stairs. There was nothing left for Harry to do but pass them. Mr. Farley cast a sleepy glance at the boy, but did not speak. He invariably treated the lad as though he were a part of the department furnishings. The slender, dark man paid no attention to him whatever.

“How can I hear his voice if I can’t get near enough to him to hear it?” was Harry’s disgusted reflection. “I’ve got to hear it, but how can I manage to?”

From behind a concealing screen of books some distance from the stairway, Harry peered at the two men. Acting on a flash of impulse, he suddenly walked boldly toward them. He had happened to recall that there was to be a sale of sets, too, along with the miscellaneous books.

“Do you want me to help you with your sets, Mr. Farley?” At the sound of the boyish voice the men at the stairway whirled about. They had turned their backs to the book department and had not heard his almost noiseless approach.

“When I do, I’ll let you know,” frowned Mr. Farley. His sleepy eyes awoke and gleamed angrily at the interruption. The Frenchman glowered reprovingly at the lad. “Go away, boy,” he rebuked. “Why haf you interropted os?”

“I beg your pardon.” There was a mocking inflection in Harry’s tone. Then he obediently removed his undesired presence to the other end of the department. He was quite ready to go for he had attained his object. The dark man had spoken, and in the voice was the inflection he had reason to remember.

“It’s the same voice,” he breathed half aloud. “Now that I know, I suppose I’d better tell Mr. Rexford about it, and let him see to it. He’ll believe me, but if I told somebody else he might not. Well, I’ve found out what I wanted to, so now I’ll get to work as fast as I can. It’s after six and I have to be out of here by eight o’clock.”

“Here, Harry,” directed a pleasant voice. “I need you.” It was Mr. Denby, the man who had charge of the new fiction, who called out. “This table is to be cleared and those books put on it.”

“All right, sir.” Harry attacked the job with vigor.

It was twenty minutes past seven when that task was finished. Harry stood eyeing his grimy hands. “I guess I’d better wash my hands,” he decided. The water faucet was situated in a small room devoted to the book mail-orders, at one side of the department, and opened into it by two doors. There was no light and as Harry did not know the situation of the switch he felt his way to the faucet in the dark.

He had washed his hands, dried them on his handkerchief, and was about to pass out through the upper door when he heard subdued voices. Two men entered by the lower door and began to converse in low tones.

“You go and get it,” drawled a familiar voice. “Here’s the set, all wrapped. Keep to the lower end of the department. I’ll wait here until you bring my stuff. Make it flat, so I can button it inside my coat. You’d better take the books out one at a time. That’s a peach of a set. It’s full morocco. If Rexford ever misses it there’ll be some yelling.”

A dark, indistinct figure slipped from the lower door, another dimly outlined figure drew close to the side of a high desk out of sight of any chance intruder, while a third boyish figure sped across the department in search of Mr. Rexford, who had announced his intention of returning that evening to direct the preparation for the sale.

“Have you seen Mr. Rexford, Fred?” Harry’s eyes blazed with excitement, as he paused for an instant to question the other stock boy whom he met coming toward him, his arms full of books.

“Nope,” was the answer. “I don’t b’lieve he’ll show up. He hardly ever comes around when the fellows are workin’ at night.”

“But he said he’d be here.” Harry’s face was full of anxious concern.

“Well, mebbe he will, then. Don’t cry about it,” jeered Fred.

Harry did not answer this jibe. He merely smiled and set off in the direction of the buyer’s office. The door stood half open, but the office was dark, except for the faint light which shone into it from the department. “He isn’t there,” muttered the boy. “I’ll have to tell someone else.” He realized that if he did not act quickly the two men would have exchanged packages and gone. To prove their guilt it was necessary to surprise them in the mail-order room.

Harry darted from the buyer’s office and collided violently with a man who had stepped into his path from between two tables.

“I beg your pardon,” he began, “I didn’t—— Oh, Mr. Rexford, I was looking for you.” The man with whom he had collided was the man he sought. “Please come quickly, or it will be too late. Two men are trying to steal some books. They’re in the mail-order room. That is, they were there, if they haven’t got away. We must slip in at the upper door without making any noise.”

Mr. Rexford followed Harry without question. To the boy it seemed an hour since he had stolen from the mail-order room on his anxious quest for the buyer. In reality not more than four minutes had passed. “I’ll stay back,” he whispered as they neared the door. “You go in.”

Just inside the upper door stood a tall filing cabinet. It effectually screened Mr. Rexford’s noiseless entrance into the room. By crouching to one side of it he could lean forward and thus view all that went on, the darkness of the room protecting him from observation. Outside the doorway Harry waited in an agony of suspense. No sound came from within the room. He wondered if the Frenchman had returned while he was hunting Mr. Rexford, if the quick exchange of packages had already been made and the two thieves had stolen away.

Mr. Rexford, however, had heard someone moving in the vicinity of the desk. He knew, if Harry did not, that one of the men was still there. Who they were he could not guess. The sight of Harry’s troubled face as he cried out to him to come quickly was sufficient to convince him of the seriousness of the situation.

It was not long before the watcher heard a stealthy footfall. Someone had entered through the lower doorway. A dark figure left the protection of the desk. “I thought you’d changed your mind about coming back,” drawled a low voice.

Mr. Rexford started in astonishment.

“It is not long—ten minutes, perhaps,” rebuked the newcomer. “Here is the portiere. The package is small. You can——”

The room was suddenly flooded with a penetrating light, revealing the Frenchman in the act of holding out a package to the sleepy-eyed salesman, Mr. Farley.

“What does this mean, Farley?” Mr. Rexford confronted the astonished pair. The man Farley turned deathly pale. The package dropped from his hand. The Frenchman evaded Mr. Rexford and leaped for the door. The next second there was a rumble, followed by a loud crash. The man had stumbled over an empty truck, sending it rumbling against a book table, while he sprawled headlong to the floor.

The noise, coupled with the man’s fall, brought several workers to the scene. The Frenchman scrambled to his feet and was about to slink off when Mr. Rexford’s authoritative voice called out from the mail-order door, “Don’t let that man get away. I want him. Take him to my office and keep him there until I come.”

Two of the salesmen hustled the man unceremoniously toward the buyer’s office. Mr. Rexford retired into the mail-order room, only to appear almost instantly with Farley. The salesman’s face was ghastly, his usually sleepy eyes were dark with fear. He walked quietly beside the buyer, however, making no effort to flee.

Mr. Rexford stopped and said something in a low tone to Mr. Denby, the man who had charge of the fiction. The salesman hurried out of the department, while the buyer motioned Farley into his office, stepped in after him and closed the door.

A little group of workers gathered at one side of the department to discuss the meaning of the scene they had just witnessed.

“I suppose they’ve been stealing. Looks like it,” advanced one young man. “Who’s that dark fellow? I’ve seen him around the department talking to Farley. He’s the last person I’d accuse of stealing. He’s been here for ten years.”

“It’s cribbing, all right enough. Here comes Prescott, the head detective,” murmured one of the men who had escorted the Frenchman into the office. “I wonder who spotted the game?”

Harry Harding might have given that information, but, instead, he stood in silence, listening to the talk that went on among the men. Glancing at the clock he saw that it was five minutes to eight. The law forbade any boy of his age to work after that hour. He was glad of it. He would go at once. He feared he might be called behind that closed door to testify against the offenders, and he shrank from doing so. He was not really needed. Mr. Rexford had caught the men in the act of exchanging stolen goods. Now the detective could do the rest. Harry lost no time in turning his night pass over to the man on the door and leaving the store behind him.

He had been gone perhaps fifteen minutes when Mr. Rexford emerged from the office and asked for him.

“He went home on the dot of eight,” reported Mr. Denby, the fiction salesman. “You know these boys have to keep within the labor law.”

Mr. Rexford smiled. “That boy has done a good deal more to-night than keep within the labor law. He’s been of untold service to Martin Brothers and to me. He has rounded up the ringleaders of a gang of thieving employees that have been profiting at the store’s expense for a long time. What I’d like to know is where he got his first clue?”