Nearly two hours later, or considerably after midnight, Nick Carter felt a hand on his arm and heard the subdued voice of Mr. Horace Carrington, the host, a portly man in the fifties, then wearing an elaborate courtier’s costume. “I want you for a few moments, Carter,” he said quietly. “Come with me.” “Anything wrong?” questioned Nick, noting his gravity. “I fear so,” said Carrington. “A lady, one of my guests, wants to talk with you. She is waiting in my private library. This way.” Nick followed him with further questions and entered the room, where the lady at once arose to meet him. She was a woman in starry black--the duplicate Night. She no longer wore a mask, however, and Nick found himself face to face with an old acquaintance, one for whom he already had done double service. She was none other than the whilom beautiful chorus girl for love of whom Lord Archie Waldmere had sacrificed his heritage and English birthrights and become estranged from home and family--now Lady Mollie Waldmere. “Good gracious!” Nick quietly exclaimed. “Is it you, Mrs. Waldmere? What has happened?” She extended a trembling hand and gazed at him with apprehensive and glistening eyes. “I don’t know,” she replied. “I cannot even imagine. I have told Mr. Carrington, and he said you were here incognito and in disguise, so I asked him to call you. I have not forgotten what you have done for Archie and me, Mr. Carter.” “Don’t mention that, Mrs. Waldmere,” said Nick. “What now is the trouble?” “I don’t know,” Mollie tremulously repeated. “I only know that I--I cannot find my husband.” CHAPTER II. A DEEPENING MYSTERY. Nick Carter was much less surprised, of course, upon learning of the mysterious disappearance of Archie Waldmere, than he would have been if he had not seen the episodes that had occurred about half past ten, and the remarkable duplication of the costume described. Naturally, too, several pertinent questions at once arose in Nick’s mind. Who was the other woman--the duplicate Night? Was Waldmere the masked man who had accompanied her from the house and departed in a limousine? Did he, in that case, know with whom he was going, or did he suppose he was departing with his wife? If not, and he went willingly with another, what motive had he in so doing? Was he guilty of a secret love affair, as Chick had suggested, and had he gone to indulge in a clandestine flirtation, intending to return within a reasonable time, only to be inadvertently detained until this late hour?