“But if there’s a tunnel from this lonely island under the lake and beneath the shore right up almost to our plant, it means that something desperate is in the wind,” reasoned Tom. “They must have resented my blundering into it as I did, and they tried to put me out of the way. After they doped me they must have carried me a long way through the tunnel, to chain me fast near this end. “Well, I’m free now, and out in the open. About noon, I should judge by the sun and by the way my stomach feels,” Tom went on, with a grim smile, for he was getting hungry and feeling a bit weak now. “I hope it isn’t more than the next day,” he went on, meaning the day following his night encounter with Ned. He looked about him. Barn Door Island was about five acres in extent, large enough, on account of its wild character, to give concealment to any number of enemies. But if there were any such here now they did not show themselves as Tom eagerly and anxiously scanned the somewhat wild landscape. “Well, now that I know where I am, though I can’t understand how or why I was put in that tunnel and chained,” mused the lad, as he looked at the iron still on his leg, “I might as well try to get back home. It’s pretty lonesome down here, and I don’t know whether I can signal any one or not. But it isn’t far to the mainland and I can swim it. Though if I’m going to do that I’d better file this iron off. No fun swimming with that bracelet on my ankle.” He looked about for a place where he could sit down and file in comfort at the remaining evidence of his recent bondage when, as he approached the shore, he saw, pulled up close to a rude dock in a little cove, a small motor boat. “Well, if this isn’t luck!” cried Tom. “There must be some picnic party here and that’s their boat. But no—wait a minute! Maybe it belongs to those men I heard talking in the tunnel. I’ll wager that’s it. And this is my chance! I’ll appropriate their boat since they treated me like a roughneck. I’ll get back home, maybe in time to stop their trick—whatever it is.” There was not much about a motor boat that Tom Swift did not know, and it took him but a few seconds to ascertain that this one was in good working order. No longer considering the need of filing off the leg-iron, Tom pushed the boat out from the dock, which was merely a few old logs and planks, and prepared to start the engine. He turned the flywheel and, almost at the first revolution after he had thrown the spark switch, the engine was in motion. But even as it glided out of the little cove Tom was aware of the presence of another craft. Around one of the points of the cove, as he guided his boat out, the other swung in, and a glance showed it to be occupied by four rough-looking men. Two of them wore masks. The faces of the other two were familiar to Tom, for they were two of his recently discharged workmen—Kenny and Schlump!