The watchers stood there with bated breath, being quite certain that this impromptu pursuit had something to do with Tommy's disappearance. Their sea sled was fast and Matthews was adept at handling it. To their dismay they saw the distance between Matthews and the other boat widening. The pace of Matthews' boat slowed; it stopped altogether. They saw Matthews tinkering with the motor. Then they saw him take up the oar and begin paddling back laboriously. He hailed a passing launch which towed him back to their wharf. Matthews' face was grim drawn as he reached his friends. They looked their mute inquiry. Matthews unscrewed the motor from its place and carried it up above the water line. Then he turned to face them. "Somebody was watching us from that boat with a pair of glasses. I caught the flash of the sun on his lenses. There was one man in the boat. I couldn't get a good look at him, he wore a floppy, big-brimmed straw hat well over his face. "My gas gave out when I went after him. This wasn't an accident or carelessness on my part either. I filled the tank yesterday afternoon. Someone punctured the tank during the night. The puppy barked during the night but he barks a lot at nothing. See!" He turned the motor over and pointed to a place near the bottom of the tank, where they saw a small hole with the ragged edge of the metal glinting with a freshness that the rest of the metal did not have. He continued: "It's not a sure thing I could have caught him, if I had gas; that was a pretty fast boat, faster than this I think." "Will you recognize the boat if you see it again?" asked Jimmy. Matthews shook his head slowly. "I'm not sure. There's any number of sea sleds on this lake just like it. That's not the important thing though. I should have taken the glasses along. When my gas gave out I could have had a good look at their motor. There may be a lot of boats like that but not many motors that can develop that speed. It will be a simple thing to attach that motor to another boat." He went on with grim irony: "That's simple enough. If we had ten thousand men we could comb the thirty-odd miles of lake and examine every motor on it, thus narrowing the search down to motors capable of a speed--why are they watching, why--" "Yes," went on McCall, "why this, and why do they want Professor Brierly to go back to New York? Why in the name of common sense New York? Is it--is it--" his features lit up. "Is it because someone is interested in seeing that Professor Brierly does not interfere in the affairs of Camp Higginbotham in the next few days?" There was no answer. Professor Brierly's bushy eyebrows were bristling. He was staring at the faces of the group unseeingly. Jimmy burst out: