"It doesn't take long to steal a motor-boat," commented the engineer.
"But I think I would have heard them start it," went on the lad. "Maybe it drifted off, though I'm sure I tied it securely."
"No, there's not much likelihood of that. There's no wind to-day and no currents in the lake. But it could easily have been towed off by some one in a rowboat and then you would not have heard the motor start."
"That's so," agreed the youth. "That's probably how they did it. They sneaked up here in a rowboat and towed the Arrow off I'm sure of it."
"And I'll wager I know who did it," exclaimed Mr. Jackson energetically.
"Who?" demanded Tom quickly.
"Those men who were sneaking around—Happy Harry and his gang. They stole the boat once and they'd do it again. Those men took your boat, Tom."
The young inventor shook his head.
"No," he answered, "I don't believe they did."
"Well, because they wouldn't dare come back here when they knew we're on the lookout for them. It would be too risky."
"Oh, those fellows don't care for risk," was the