Suddenly, Bentham had confided to Carter that he was worried over certain midnight visits that had been forced upon him, and instantly the great criminologist was deeply interested. “Did your burglar--or burglars--get away with anything?” he asked. “There is only one of him. At least, I think so. I never have had a clear view of his face. He is a slim, active sort of man, dressed in an ordinary dark business suit, with a soft hat pulled down over his eyes. The hat has always prevented my seeing as much of his features as I should like.” “There are many thousands of slim, active men, in dark business suits and soft hats, moving about Greater New York,” remarked Nick, between puffs at his cigar. “True,” conceded Bentham. “But you know, as well as anybody, that every human being has certain peculiarities of movement, attitude, and poise, that are not exactly the same as those of anybody else. There is a sort of what I may call ‘atmosphere’ about each one of us--an aura--that distinguishes us from all our fellows. You know that, Carter?” The detective nodded. “Yes, professor. That is pretty well understood by most persons, I think. Well, we’ll say it is only one particular burglar who favors you with his company in this way. What I asked is whether he steals anything.” “He never has yet. But I think that is because I never leave valuables lying about the room. I never carry much cash in my pockets--have no use for it unless I am going away somewhere--and my watch is always under my pillow.” “And why have you never got up to argue matters with him?” “Because I can’t. He seems to hypnotize me.” “Then there _is_ a psychological influence?” smiled Nick. “To that extent, yes. But I do not believe it is that that awakens me.” Nick Carter took his cigar from his mouth, and, with a careless gesture, knocked off the ash into a silver tray on the table. “Well, that is of not much consequence, after all,” he said. “What is the fellow after? He must have some purpose in coming three separate times, only a night or two apart. You say you don’t know how he gets in?” “Haven’t an idea. The doors and windows are all locked at night before we retire, and we find them the same way in the morning.” “What servants have you?” “Only two maids, besides the boy who does odd jobs, such as polishing brasswork, sweeping the front steps, and waiting on the cook. He sleeps out of the house. My daughter lets him in early in the morning. There is an electric contrivance, operating from her bedroom, which opens the side gate, and also connects with the lock of the back door to the kitchen.” Nick Carter stopped smoking and looked hard at the professor. He was interested in this mechanical device. “I should like to see that electric connection,” he said. “Can you show it to me?” “Certainly. Wait a moment.” Bentham went out of the room. When he returned he smiled apologetically.