WHEN Richard Duvall returned to consciousness, an hour later, he lay upon a couch in Mr. Stapleton's library. A doctor, hastily summoned, was bending over him. Mr. Stapleton sat grimly in an arm chair. There was no one else in the room.

"My wife! Is she here?" the detective cried, as he tried to rise.

The doctor pushed him gently back. "Compose yourself, Monsieur," he said in a soothing voice. "You are not badly hurt. Merely stunned for the moment. A slight cut—that is all. You will be quite yourself again in half an hour."

"But my wife!" He gazed eagerly about the room.

"What do you mean, Duvall?" inquired Mr. Stapleton, calmly. "Why do you think your wife is here?"

"A trace of delirium. He will be all right in a few moments. Very usual in such cases," the doctor whispered.

"I heard her voice. She called to me by name, just as that fellow struck me."

"My dear sir, your mind is wandering. Compose yourself, I beg." The doctor attempted to press his patient back upon the pillows.

Duvall passed his hand over his forehead, completely bewildered. "I could have sworn I heard her voice," he cried.

"It was Miss Goncourt, the young woman from the Prefecture, that you heard, Duvall," remarked Mr. Stapleton quietly. He did not tell the detective that Grace, on recovering from her faint, and learning from the doctor that Richard's wound was a superficial one only, and not at all serious, had sworn them both to secrecy, on the plea that the matter was a purely private one, and likely to cause her great unhappiness if divulged. Mr. Stapleton had agreed, but had done so only upon her agreeing not to acquaint the police with his plans for the following night.

She had suddenly conceived a violent animosity toward these fellows who had not only baffled both her husband and herself, but had made the former a victim of a dangerous assault. She was determined to go to work in desperate earnest, to capture them, or locate the child, before the following evening. She had promised Mr. Stapleton not to acquaint Monsieur Lefevre with the plan for returning the child which the man with the black beard had proposed. The situation put her on her mettle. She determined to get at the bottom of the whole affair before another twenty-four hours had passed. Upon leaving the house she called a taxicab, and at once ordered the chauffeur to drive her to the point on the Versailles road where, according to Valentin, she had been placed in the automobile after her interview with the kidnappers. Here, she believed, lay the starting point of the whole mysterious affair.

Duvall, his consciousness returning, insisted upon getting up from the couch, and going to work with equal determination. The way in which he had been checkmated, in the whole affair, roused him, as well, to desperation. His professional skill, upon which the banker had set such great store, seemed to have deserted him. He felt humiliated, ashamed. In three days, he had accomplished nothing whatever. It was galling in the extreme.Mr. Stapleton's explanations of his hallucination regarding his wife he accepted as true. The resemblance which Miss Goncourt bore to Grace, together with his constant thoughts of her, were, he argued, no doubt responsible for it. The blow upon the head made his recollections of the moments immediately preceding and following the assault extremely hazy. He put the matter out of his mind, and set to work with renewed energy.

So far, it seemed, he had met with but a single clue of any importance,—the cigarette with the gold tip which he had found in the Bois de Boulogne. He determined to follow this clue until he arrived at some definite result.

As soon as the doctor had departed after dressing the wound in his head, Duvall took a stiff drink of brandy, and, sitting down with Mr. Stapleton at the latter's desk, began to reconstruct, as far as he could, all the details of the kidnapping. He spoke his thoughts aloud, taking Mr. Stapleton into his confidence, since in this way he could most readily get his ideas into concrete form.

"Mr. Stapleton, I am, I confess, greatly humiliated at the progress, or lack of progress, which I have made in this case so far. I have made up my mind, however, to get these fellows, if it takes me the rest of the summer."

"You will have to work more quickly than that, Mr. Duvall," observed the banker coldly. "I have made arrangements to recover my child by tomorrow night."

"You are going to buy these rascals off, then?"

"Yes."

"How?"

"I decline to say. I've had enough interference with my plans already. Neither you nor the police have accomplished anything. Miss Goncourt knows what I propose to do; but she has given me her word not to interfere. If you are to accomplish anything, it must be before eight o'clock tomorrow night."

"Very well. I will make my plans accordingly."

"What do you propose to do?"

"That I cannot say, at the moment. I think, however, that I shall first try to find out who it is that smokes these gold-tipped cigarettes." He drew the fragment of cigarette which he had found from his pocket, and placing it on the desk before him regarded it critically.Mr. Stapleton gave a grunt. "What are they, Exquisites?"

"Yes. How did you know?"

The banker laughed. "Easy enough. My wife smokes them."

The detective looked up quickly. "Indeed! Brings them from America with her, I suppose."

"Yes."

Duvall began mentally to check off, in his mind, the various persons who might have used the cigarette which lay before him. Valentin, he now believed, was out of the question. His presence in the automobile, with Grace, the night before, indicated that he had nothing to do with the kidnappers.

There remained Mrs. Stapleton. Duvall had talked with her—seen her grief. He was too shrewd a judge of human nature to think for a moment that it was assumed.

Who else? Suddenly an idea flashed into his mind. He wondered that he had not thought of it before. The nurse! He recalled vividly the marks he had observed on the dresser in the woman's room in New York.

"Is Mary Lanahan in the house?" he inquired of Stapleton."Yes. Why?"

"Kindly have her come here."

Mr. Stapleton pressed a button on his desk in silence. In a few moments, the nurse had been brought to the room by one of the other servants. She was haggard with grief and fear.

Duvall requested her to be seated, and began to ask her a number of apparently unimportant questions regarding the kidnapping.

She answered them frankly enough, although it was clear that she was very ill at ease.

Presently Duvall got up, and, calling Mr. Stapleton to one side, asked him, in a low tone, to detain the nurse in the library for a few moments. He wished to search her room.

"But it has already been thoroughly searched by the police."

"I know. But I must search it again. It will require but a few moments."

Stapleton nodded. "I will wait for you here, Mr. Duvall," he said. "Mary, you will wait, as well."

The nurse's room was on the third floor, in a rear building. Duvall found it, after some slight difficulty, with the assistance of one of the other servants.He seemed, on entering the room, to have but one object in view. He went at once to the mantel, and, taking from it the two small bottle-shaped vases which stood upon it, shook them both vigorously. A faint rattling sound came from the second. He turned it upside down upon the palm of his hand, and there tumbled out a quantity of ashes, and the butts of several partly smoked cigarettes. With a quiet smile he replaced them in the vase, and returned to the library.

"Mary, you may go now," he said.

When the woman had gone, he turned to Mr. Stapleton. "It was Mary Lanahan herself who smoked the cigarette which I found in the grass," he said.

"Well, what of it?" The matter seemed to the banker to be utterly without significance.

"She had, no doubt, stolen them from Mrs. Stapleton."

"Very likely. Not a very serious matter, however."

"No. But the question now arises, Why did she turn the box over to Valentin, and subsequently ask him to destroy it?"

"I cannot imagine.""And why, later, were these cigarettes stolen from Valentin, as I understand they were?"

"It's too much for me. What do you make of it?"

"I have a theory, Mr. Stapleton; but I cannot say just what it is—yet. By the way, where is your man, FranÇois, tonight?"

"He is visiting his people, somewhere in the suburbs."

"Ah! Then I would like to search his room, as well."

"Go ahead. You will find nothing, I fear. The police have gone over it with a fine-tooth comb." He rose. "Come along, I'll go with you."

The room occupied by the chauffeur was at the very top of the house, with two windows opening through the slanting mansard roof. One of these, Duvall noted, commanded a view over the houses adjoining toward the north, beyond which could be seen the Avenue du Bois de Boulogne. A second window, toward the south, commanded an extensive view toward Passy.

Mr. Stapleton, puffing because of the unaccustomed stairs, sat down upon the bed. "I cannot imagine what you hope to find here, Duvall," he grumbled.The detective made no reply, but began a systematic inspection of the room. One of the first objects which attracted his attention was an ordinary electric searchlight, of the pocket variety, lying on the man's dresser. He picked it up, and examined it carefully.

"I got it for FranÇois," observed Mr. Stapleton, "so that he could examine the car, at night, in case of any accident or repair."

"Of course. Very useful, too. But why, I wonder, does he keep it here in his room, instead of in the garage?"

"Possibly to light himself up the stairs, at night," said Stapleton.

"Then I should think he would have it with him," remarked Duvall, dryly. "Wouldn't be of much use to him tonight, for instance." He was about to put the thing down, when his attention was attracted by two objects, hanging one on each side of the dresser, from its two uprights. They were apparently Christmas tree ornaments, made of thin glass, and they hung from the back of the dresser by means of two bits of ribbon.

They seemed at first glance to be merely souvenirs of some party, some entertainment, which the chauffeur had preserved as mementos of the occasion. They were shaped like little cups, with a paper fringe about the top, to which the gay ribbons were attached. Duvall had seen such ornaments often before, at Christmas time. They were intended to be hung from the tree by their ribbons, and were filled with small candies or bonbons. He had almost passed them by, when something in their colors caused him to pause. One was a deep blue, the other an equally deep red. He examined the wooden uprights of the dresser with great care. All along the top of the dresser at its back was a heavy coating of dust. The top of the uprights, over which the loops of ribbon which supported the little baskets had been passed, contained no dust whatever.

Evidently the baskets had been taken down, and that too quite recently. For what purpose? he wondered. Suddenly he had an inspiration. He took down the little blue basket, and quickly placed it over the end of the searchlight. It fitted perfectly, the paper collar at its top holding the glass hemisphere snugly in place.

Mr. Stapleton was watching Duvall without particular interest. Suddenly the detective pointed the searchlight toward him and pressed the button which threw on the current. Mr. Stapleton started back, as his face was flooded with a beam of brilliant blue light.

Duvall replaced the little basket in the same position in which he had found it, and laid the searchlight upon the dresser. "Rather neat, isn't it?" he exclaimed.

"What do you make of it?" asked the banker.

"Your man FranÇois evidently is in the habit of making signals," the detective replied, laughing. He was beginning to feel hopeful. The search of the two rooms was bearing fruit.

For the next half-hour, Duvall went over the contents of the chauffeur's room with the utmost care. He removed and replaced, just as he found them, the contents of the dresser drawers. He opened a small wooden trunk which stood at one side of the room, and examined its contents minutely. He explored the closet, looked behind the pictures, sounded the walls. Nothing further of an unusual nature rewarded his efforts. Still he seemed unsatisfied.

"What more can you hope to find, Mr. Duvall?" inquired the banker, who had begun to find the proceedings tiresome.

The detective stood in the center of the room, and glanced about in some perplexity. "I had hoped to find one thing more," he said; "but I am afraid it isn't here."

Suddenly he strode over to the mantel, upon which stood a small nickel-plated alarm clock of American make.

"This clock doesn't seem to be going," he remarked, then whipped out his magnifying glass and carefully studied the brass handle which projected from the back, by which it was wound up. "It hasn't been wound for several days, either. The back is covered with dust." He picked up the clock and tried to wind it; but the handle resisted his efforts.

In an instant he took out his knife, and a moment later was removing the screws which held the metal back of the clock in place.

Mr. Stapleton watched him curiously. Duvall's methods savored, to him, of the accepted sleuth of fiction. He took little stock in the tiny clues upon which the whole modern science of criminology is built.

In a few moments the detective had removed the screws and lifted out the rear plate of the clock. As he did so, he gave a grunt of satisfaction. A small pasteboard box fell out upon the mantel."What is it?" asked Stapleton.

"The box of cigarettes," remarked Duvall, as he opened it. "There are three missing. I shall take a fourth." He selected one of the paper-covered tubes, placed it within his pocketbook, then thrust the box back into the clock, and rapidly replaced the metal plate.

"I don't think there is anything further to be done here, Mr. Stapleton," he remarked. "I think I'll be getting along to my room. Tomorrow I shall be quite busy."

He stopped for a moment, on his way out, to glance from the window which faced toward the north. Between the buildings and trees ran the Avenue du Bois de Boulogne, its course illuminated by many street lamps, and the flashing lights of passing motor cars. Duvall gazed intently at the scene before him for a few moments, then turned to the door, and, accompanied by Mr. Stapleton, descended the stairs.

As he was about to leave the house, the banker, who evidently had something on his mind, stopped him.

"Mr. Duvall," he said, earnestly, "I would like very much to know what you intend to do.""I'm going to catch these fellows, if I possibly can," the detective replied, earnestly.

"What steps do you propose to take?"

"I cannot exactly say—yet. Why do you ask?"

"I'll tell you. The fellow who was here tonight, the one with the black beard, is coming to see me tomorrow night, at eight o'clock. I cannot tell you more than that. I did not intend to tell you that much—but I am obliged to do so."

"Obliged! Why?"

"Because I want your promise that you will make no attempt to stop him. If I had said nothing, you might have watched the house, and, upon recognizing the fellow as the one who was here tonight, have placed him under arrest. I want you to do nothing to interfere with either his coming or his going. He will be safe, after he once leaves the Arc de Triomphe in his automobile."

"But the police?"

"They know nothing of the matter. Miss Goncourt has given me her word to remain silent. She has even agreed to have the men on watch about the house withdrawn. Both you and the police may do your best to catch this man, after I have carried out my compact with him; but until then I want you to keep your hands off."

Duvall was silent for a moment. "Very well, Mr. Stapleton, I shall do as you say. In fact, to assure you that I am carrying out your wishes, I will agree to remain here with you, at the house, throughout the evening."

"Good! I shall expect you. Good night."

"Good night." Duvall left the house, and went at once to his hotel.

Here, a few moments later, he seated himself in an easy chair, and taking from his pocket the cigarette which he had secured in the chauffeur's room, regarded it critically.

After some little time, he took a match from a box upon a nearby table, and, placing the gold tip of the cigarette between his lips, carefully lit it.

He drew the smoke into his lungs, inhaling it deeply. Once—twice—three times he repeated the operation, then threw himself back into his chair, and, closing his eyes, sat buried in thought. In his preoccupation, he allowed the end of the cigarette to fall unheeded to the floor.

After many minutes he opened his eyes and started up. "I've got it!" he cried, and, picking up the half-burned cigarette from the floor, threw it carelessly into the fireplace.

Then he sat down at his table, drew out a sheet of paper and a map of the city of Paris, and began to make a series of drawings and calculations that occupied him far into the night.