"As you know," he said, "the partition that divides madame's private apartments from the shop does not extend to the ceiling; there is a gap of some three feet. I had previously noticed the cheval-glass in the bedroom; it was a natural presumption that L. Hernandez would take her stand in front of it while engaged in making her toilet. Now this glass is tilted at a sharp angle, and consequently the reflection must be projected upward to a particular point on the ceiling. Supposing a small looking-glass to be fixed at this point, the rays impinging upon it will be cast downward and ON OUR SIDE OF THE PARTITION, for the angle of reflection is always equal to that of incidence. We have, therefore, only to place in position a second cheval-glass, arranged at the proper inclination, to obtain a reproduction of the original image, although, of course, it will appear to us as upside-down. I have only to add that the day you escorted madame to Police Headquarters I took the opportunity to fasten a small mirror on the ceiling, trusting that it would not be noticed. Nor was it; the trap worked perfectly--an optical siphon, as it may be called--and the secret was mine." "And now?" "Wait until to-morrow," said Indiman. For the fiftieth time the game of solitaire was in progress, and on this occasion it seemed as though the combinations were actually coming out. Remember, that in the final fall of the cards it was necessary that they should be in four packs, headed by the ace of clubs, king of diamonds, queen of spades, and knave of hearts. Already the first two ranks had been completed; it all depended upon the disposition of the few remaining cards. "The queen of spades is buried," said L. Hernandez, with a sneer. "You have failed again." "I think not," replied Indiman, calmly. "I am sure that the last card is the knave of hearts." This was my cue. I stepped to the door and made an imperceptible signal to Brownson, who, with two other plain-clothes men, was lounging in a door-way across the street. They seemed eternally slow in obeying; I felt the muscles in my throat contracting with nervous excitement as I turned again to watch the solitaire. But two cards remained to be played; they lay face downward upon the table. If the upper one were the queen of spades, the packets would be completed in their proper order and the solitaire would be made; if it were the knave of hearts, the game would again be lost. Slowly--oh, so slowly--Indiman turned the first card. "Knave!" shouted L. Hernandez, exultingly. Then she stopped and went white. It was not the knave of hearts, but the queen of spades, and over it had been pasted a small carte-de-visite photograph--that of a man dressed in the coarse uniform of one of the Russian penal settlements. With lightning swiftness Indiman leaned forward and twitched the wig from L. Hernandez's head; the man himself sat there before our eyes.