“Probably not,” said Nick. “I am not far enough in the case to understand it myself. We are already engaged on one case of blackmail in which the Brown Robin figures as a woman. Now you give us one in which it figures as a man. “The Brown Robin has given a good deal of trouble in Chicago, Boston and Philadelphia without being detected. “It has just begun operations in New York. I imagine your case is the first one of its operations, and the other we have the second. “Whether it is a he or a she, or a gang, it is bold, audacious and skillful, working in a new way.” “By the way, chief,” asked Patsy, “have you received another letter from the Brown Robin?” “Yes; why do you ask?” “Because this fellow I followed sent you one.” Nick picked a letter from the table and handed it to Patsy. It read: “My Dear Uncle: Really, you are much better than I supposed. It is worth while working against you. You’re not easy, but keep me at work. What a dance you gave me this morning. And your Patsy is a regular laloo. He ran me down and cornered me this morning. If he had dared to arrest me he would have done so, but he had no right to do that, so, of course, he didn’t. I slipped away from him only by accident. The above is only by the way. I write to say that you are not serving Papa Cary well. Drop him for his own sake. Even if you do stop him from giving me more, I’ll ruin him. That is my rule. His safety is in submitting to me. “The Brown Robin.” Patsy folded the letter, and handed it back to Nick, saying: “He wrote another to the other.” “Who?” Patsy wrote the name of Alpheus Cary on a slip of paper, handing it to Nick. “Ah! I must know what it said,” said Nick, as he glanced at it. Turning to Mr. Mountain, Nick said: “One of the peculiar features of this affair is the frequent and impudent letters that are written to me. “Until you came with your story, I was at a loss to understand the reason of them. I do now. Your case is the big one. While it is being worked the Brown Robin would have us think that the other case is the only one it is working on. “It is quite ingenious and a new way of working. Leaving a trail open on the second, they will carefully make those to the first blind. “Now, Mr. Mountain, return to your office. Another aid of mine will call on you as soon as he can. His sole business will be to study your appearance. Give him every opportunity. “If you receive another letter, let him have it. If you receive a notice from the Brown Robin to go to any particular place, tell him of it. That I must know of at the earliest moment. “Now, Patsy, Chick is over somewhere in Seventeenth Street. Find him and send him to Mr. Mountain’s office. Now get away, please, both of you, for I must go out.” Mr. Mountain returned to his office, feeling a weight off his shoulders, since the celebrated Nick Carter had the case in hand. Patsy hurried off to find Chick.