While Riley and Bob and Hugh covered the three prisoners, the officer went rapidly from one to another and took a revolver from each one of them. He also examined their other pockets, but finding no additional weapons returned to his post by the door. While this little drama was being enacted Bob had a chance to look about the room. It was scantily furnished, a table, four chairs, and a shelf along the wall constituting its equipment. On the shelf were a dozen or more bottles that looked as if they might contain chemicals; a square black box stood on the table and also a brass spring and what resembled a cord hanging from one side. Bob decided it was a bomb. From a nail in the center of the ceiling a small alligator was suspended by its tail. Bob recognized the missing Percy, and decided that this must be the headquarters of the gang that had used an alligator as its symbol, and traced a picture of it on all the notes and warnings they sent out. While the furnishings of the room were interesting, the three men captured were far more so, and as Bob saw one of them he experienced a distinct shock. The first was a man with dark hair, weighing perhaps one hundred and fifty pounds, and having a close-cropped mustache; the fake detective beyond a doubt. The second was a thin, wiry individual with a beard, and a swollen, red nose. He was the man who had escaped from his and Hugh's hands at the factory, Bob decided. His nose was swollen where Hugh had hit him. This must be the man who had set off the bomb. The third prisoner was the one who furnished the surprise to Bob, however. He was a man Bob had known for years, and liked, admired, and trusted as well. He was Karl Hoffmann. "Well," exclaimed Sergeant Riley, "it looks as if you men was through with your work. Get out your handcuffs, Marshal." Up till now not one of the prisoners had spoken. When they saw the manacles being brought out, however, they shifted uneasily and Karl spoke. "Bob," he said. "This is all a mistake." Bob would have liked to believe him but before he had an opportunity to say anything Sergeant Riley spoke up. "Perhaps it is a mistake," he exclaimed. "We can talk that over down at the police station better than here, however." There was now little left to do. The handcuffs were quickly attached to the prisoners' wrists and Hugh was sent to the second floor to telephone for the patrol wagon. The prisoners were marched downstairs, and Mr. Cook and the other policeman were summoned. Mr. Cook was as shocked as Bob had been to see Karl Hoffmann among those who had been captured in the raid. There was nothing for it, however, but to see him loaded into the patrol wagon and driven away to police headquarters. CHAPTER XXVIII CONCLUSION Mr. Cook, with Bob and Hugh, returned home. They had been in the house only a few moments when the telephone rang, and Mr. Cook answered it to find Sergeant Riley on the wire.