Henry Robinson, the caretaker of the Tower Mansion, was the father of one of their closest chums. Perry Robinson, nick-named "Slim", was to have accompanied them on their jaunt to the woods that day but had failed to appear. The reason was now evident. But that Henry Robinson should be accused of the robbery seemed absurd. The boys had met Slim's father and he had appeared to them as a good-natured, easy-going man, the soul of truth and honesty. "I don't believe it," whispered Frank. "Neither do I," returned his brother. "What makes you suspect Robinson?" asked Mr. Hardy of Hurd Applegate. "He's the only person besides my sister and me who ever saw that safe opened and closed. He could have learned the combination if he kept his eyes and ears open. I believe he did." "But is that your only reason for suspecting him?" "More than that. This morning he paid off a note at the bank. It was a note for nine hundred dollars, and I know for a fact that he didn't have more than one hundred dollars to his name a few days ago. The Robinsons have been hard up, for they had sickness in the family last winter and Henry Robinson has had a hard time meeting his debts since then. Now where did he raise nine hundred dollars so suddenly?" "Perhaps he has a good explanation," said Mr. Hardy mildly. "It doesn't do to jump at conclusions." "Oh, he'll have an explanation all right!" sniffed Mr. Applegate. "But it will have to be a mighty good one to satisfy me." "Luckily, he'll not have to satisfy Mr. Applegate, but will have to convince a jury--if it gets that far," whispered Joe in his brother's ear. The automobile was speeding up the wide driveway that led to Tower Mansion, and within a few minutes it drew up at the front entrance. Mr. Applegate dismissed the driver, and Mr. Hardy and the two boys accompanied the eccentric man into the house. Nothing had been disturbed in the library since the discovery of the theft. Mr. Hardy examined the open safe, then drew a magnifying glass from his pocket and with minute care inspected the dial of the combination lock. Then he examined the windows, the door-knobs, all places where there might be finger-prints. At last he shook his head. "A smooth job," he observed. "The fellow must have worn gloves. Not a finger-print in the room." "No need of looking for finger-prints," said Applegate. "It was Robinson--that's who it was." "Better send for him," advised Mr. Hardy. "I'd like to ask him a few questions." Mr. Applegate rang for one of the servants and instructed him to tell Mr. Robinson he was wanted in the library at once. Mr. Hardy glanced at the boys. "You had better wait in the hallway," he suggested. "I want to ask some questions, and it might embarrass Mr. Robinson if you were here." The lads readily withdrew, and in the hallway they met Henry Robinson, the caretaker, and his son Perry. Mr. Robinson was calm but pale, and at the doorway he patted his son on the shoulder.