"I was not certain of it. I intended to have the fragment I had found analyzed. When I discovered the cigarettes in François' room, you will remember that I took one of them. I smoked that cigarette, before going to bed that night. It produced exactly the sensations that Mary Lanahan must have felt. I floated away in the land of dreams for over half an hour, and came to with no recollection whatever of the passage of time. It is a remarkable drug, but an extremely dangerous one.
"After that, the case became simple enough. I knew at once, beyond any question, that François was one of the kidnappers. My plans last night would have worked perfectly, but for the chauffeur's accidental discovery of me, hiding in the closet. Had that not happened, the boy would have been returned, according to program, and François I had safely in my hands."
"But we wouldn't have got the others," laughed the Prefect. "You must thank your wife for that. Vernet has told me how the kidnappers outwitted you at the Avenue Malakoff. The car from which the signal apparently was made contained a well known stockbroker, who knew nothing of the matter at all. He merely happened to be passing the Avenue Malakoff at the precise moment when the signal was given to François."
"You are mistaken, Monsieur," observed the detective, quietly. "The signal was undoubtedly made from that car; not by Monsieur Lemaitre, I will admit, but by his chauffeur. He has admitted to Vernet that a stranger paid him fifty francs to do so, on the plea that it was some signal to a woman. The man knows nothing of the affair, beyond that."
As he finished speaking, there was a ripple of laughter from the hall, and Mrs. Stapleton, Madame Lefevre, and Grace came in.
"We have been debating a most important question," said Mrs. Stapleton, with an assumption of extreme gravity, "and we beg that you, Monsieur Lefevre, will be so good as to decide it."
"What is this question so grave, Madame," inquired the Prefect, rising, with a smile. "I am all impatience to hear it."
"The question is this, Monsieur Lefevre: Which deserves the greater credit for the recovery of my boy—Mr. Duvall, or his charming wife?"
The Prefect stepped forward, placed one hand affectionately upon Duvall's shoulder, and with the other grasped Grace by the arm.
"The question you propound, Madame," he said, looking from the detective to his wife with a smile, "is easily answered. The credit belongs equally to both. And that, my children, is as it should be. This affair, so happily terminated, has taught me one important lesson. It is this: The husband and the wife should never be in opposition to each other. They must work together always, not only in matters of this sort, but in all the affairs of life. I attempted a risky experiment in allowing these two dear friends of mine to attack this case from opposite sides. But for some very excellent strokes of luck, it might have resulted most unhappily for all concerned. Hereafter, should Monsieur Duvall and his wife serve me, it must be together, or not at all." He turned to Grace. "I feel that I owe you both a great debt, my child, for having once again so rudely interrupted the course of your honeymoon. What reparation can I make? Ask of me what you will."