It was truly strange, he thought, the course of events leading up to this moment. After a considerable stay in the wilds of Michigan he had returned to the city of Chicago. On his arrival he had gone at once to the shack. The shack, on Grand Avenue, as you will know if you have read "Arrow of Fire," was occupied by Drew Lane, a keen young city detective, and such of his friends as happened to be about. To his great disappointment, Johnny had found the shades down, the door locked. "Must be away," he told himself. At once he found himself all but overcome by a feeling of loneliness. Who can blame him? What is lonelier than a city where one has not a single friend? Johnny had other friends in Chicago. Doubtless he would chance upon them in time. For the present he was completely alone. "Be rather amusing," he told himself, "to try going it alone. Wonder how long it will be before someone will slap me on the back and shout, 'Hello, Johnny Thompson!'" Having recalled the fact that at noon on every Tuesday of the year a rather unusual auction was held, he had decided to dispel his loneliness by mingling in the motley mob that attended that auction. There for an hour he had watched without any great interest the auctioneer's hammer rise and fall as he sold a bicycle, a box of clocks, a damaged coffin, an artificial arm, three trunks with contents, if any, two white puppies in a crate and a bird in a cage--all lost or damaged while being carried by a great express company. It was only when the Three Black Boxes were trundled out that his interest was aroused. "This," he heard the auctioneer say in a low tone to a man seated near, "is a professor's library. He hasn't come to claim the shipment, so we are forced to sell his books." "A professor's library! Poor fellow! What will he do without his books?" Johnny had said to the man next to him. "A professor without books is like a juggler without hands." "A professor's library." The words had intrigued him. The very word professor had a glorious sound to him. They had been so good to him, the professors of his college. Without more than half willing it, he had begun bidding on those three heavy black boxes filled with books. In the end they were his, and his pockets were all but empty. After the affair was over he had hunted up the auctioneer and secured the name and address of the professor. "I'll sell the books back to him," he said to the auctioneer. "Surely he _must_ have some money, or will have in a month or two." "Well, maybe." The auctioneer had shaken his head. "Lots of folks pretty poor these days. Too bad!" "And this," Johnny told himself as he continued to pace the floor of that mysterious room, "is the professor's house. Seems more like the haunts of an evil genius."