He turned to the uniformed attaché and calmly surveyed him, ere he answered quietly, and in a tone very much unlike that of his natural voice: “All right! Go ahead!” Without a word, the attendant preceded him to the wide, carpeted staircase leading to the corridor at the back of the private boxes. He stopped at number thirty-six, which was painted on the box door in gilt figures. Nick Carter took his seat in the box, and leaning his strong chin on his hand, watched with interest the moving throng on the floor below. “I don’t believe Martin or any of the gang are here,” muttered Nick, after half an hour’s steady contemplation of the promenaders and dancers. “He’s heard that I’ll be here, and he’s keeping dark still. Well, I’ll get him yet. I shall stay for a couple of hours, anyhow. He and Lawton, or some of the gang, may come later. They’re going to get rid of some of those hundreds to-night, unless that informant of mine is a liar or very badly mistaken.” There was a little disappointment in Nick Carter’s bosom. This man, Shoreham Martin, was a man who had always covered his tracks successfully. At the same time, there was little doubt on the part of Nick Carter that he was the prime mover in one of the most audacious and successful counterfeiting organizations in America. “If I don’t get Martin to-night, it will only be putting off the happy day,” continued Nick, to himself. “I have that comfort for my soul.” A soft tap-tap at the door made him swing around and look into the gloom at the back of the box. The tapping was repeated, and Nick got up and opened the door. A slender girl, in the black-spangled robes of a “Queen of Night,” stepped inside and closed the door. She was masked, but Nick could see a beautiful chin and white temples, which satisfied him the “Queen” was young. Probably, also, attractive of face. “I beg pardon----” he began. “Hush!” She held up a finger for silence and motioned toward the curtains at the front of the box. “Draw them together, quick!” she whispered. Nick Carter had not the slightest idea what this was all about. But the mystery of it appealed to his love of adventure, and he closed the curtains at once. “Be careful, Marcos,” went on the girl, in a tense, hushed voice. “They know you are here.” “The deuce they do!” thought the detective. “I have had a warning,” she continued. “They are going to send you up something to drink. But you must not take any of it.” Nick Carter stared down at the masked face, and noted the general poise of the slight figure with admiration. Mingled with it was perplexity. “I am sure you are making a mistake,” he told her. “Who do you think I am?” “Don’t be foolish!” she rejoined impatiently. “I tell you there is danger. I told you not to come here. But you insisted. Now see what has happened. Don Solado and Miguel have recognized you already.”