“Mr. Richard F. Mountain: Contrary to my custom, I gave you two days to comply with my demands. Then I thought you asked for time to gather the money required. Reviewing our talk, I see now that you made no promise. I have been lax. I shall not be again. To-morrow you must be prepared to comply. I shall call you to a place to pay the money. Be prompt in your coming. But heed this. Do not call in the services of Nick Carter. Do not talk to him at all. “The Brown Robin.” Holding the letter in his hand, Nick asked: “How was this demand made?” “By a young man who called on me at my office yesterday afternoon.” “What name did he give?” “None. He approached when I was engaged with some people I was doing business with, merely saying: “This is a copy, but important enough to demand your immediate attention.” “I read it, of course, and, getting up from my seat, took him aside, demanding to know what was wanted. “His answer was that he was acting for another person, who wanted fifty thousand dollars for the original. Situated as I was, surrounded by people who were at the time placing financial trust in me, I could do nothing but fight for delay and postponement.” “I see,” said Nick. “Now, have you any idea who this young man was?” “No.” “Nor who it is he says he represents?” “No knowledge.” “Do you suspect any one?” “Well, I hardly know how to reply. I had a typewriter—a young woman in my employ, who left me suddenly just before I missed that paper. Time and time again my mind has gone back to her in suspicion with nothing to support it. Her name was Alberta Curtis.” “Have you heard of her since she left you?” “In a way, immediately after her disappearance. She was a Southern girl of a good but impoverished family. She eloped with a married man. That was the cause of her leaving me. I heard of it from her family, who cast her off for the act.” “With whom did she elope?” “I only know his name—Charles Stymer.” Just then Patsy came in, and Nick sent for him. “This is Patsy Murphy, Mr. Mountain,” said Nick. “One of my most trusted aids. I want to question him on some business he has on hand.” Turning to Patsy, he asked: “Did you follow your man?” “Yes. He gave me a chase, too.” “Did you get close to him—close enough to know what he looks like?” “I had a talk with him.” “Describe him to me?” Patsy gave an elaborate description of the man that had figured before him both as George Vernon and Harold Stanton. As Patsy talked, Nick, closely watching Mr. Mountain, saw him show signs of increasing excitement, until he finally burst out: “Why, he is describing the very man who called on me yesterday.” “Then,” said Nick, with a smile, “the Brown Robin is both a man and a woman.” “I do not understand you,” said Mr. Mountain.