"They're laying-to—waiting for us, I guess."
"They won't have long to wait," declared Frank grimly.
The Gull was swiftly slipping through the water. In a little while it was almost abeam of the craft towing the mysterious motor boat. Frank threw her head up into the wind, and, as he did so a voice from the other sailboat hailed him.
"Gull ahoy! Are you trailing us?"
It was the mysterious man calling, and he was standing on the rail.
"Yes, we are," answered Frank boldly.
"Well, what do you want?"
"We want to find out who you are, what you have to do with a boy named Paul, why you have his motor boat in tow, and why you entered our house like a thief in the night."
"Hu! That's a lot of questions. And I suppose you think they'll be answered," commented the man, in sneering tones.
"I do," said Frank calmly. "Where are you going with that boat?"