keys," and Andy stuffed the money back in his pocket. Tom did not answer. He was puzzling over a queer matter and he wanted to be alone and think. He turned aside from the red-haired lad and walked toward his motor-boat.
"I'll give you a surprise in a few days," Andy called after him, but Tom did not turn his head nor did he inquire what the surprise might be.
Mr. Swift was somewhat puzzled when his son related the outcome of the key incident. He agreed with Tom that some one might have found the ring and kept it, and that the same person might have been the one whom Tom had surprised in the boathouse.
"But it's idle to speculate on it," commented the inventor. "Andy might have induced some of his chums to act for him in harming your boat, and the key advertisement might have been only a ruse."
"I hardly think so," answered his son, shaking his head. "It strikes me as being very curious, and I'm going to see if I can't get at the bottom of it"
But a week or more passed and Tom had no clew. In the meanwhile he was working away at his motor-boat, installing several improvements.
One of these was a better pump, which circulated the water around the cylinders, and another
