“There may be—I’m not sure,” was the answer in a low voice. “Wait a minute.”
Tom tiptoed softly to the door, opened it suddenly, and then uttered an exclamation of disappointment.
“What’s the matter?” asked Ned again.
“He skipped,” answered Tom.
“Who?”
“The fellow who was outside that door trying to overhear some of my secrets and find out about the Air Monarch,” was Tom’s answer.
“Spies?” exclaimed Ned.
“That’s about it. Ever since I first started on this new idea and began work on the model and the craft itself, I’ve had a sneaking idea that I’m being spied upon. I am sure of it now. Somebody was listening at the keyhole, but they heard me coming and skipped.”
“Who is it?” asked Ned.
“That’s what I’ve got to find out. Keep quiet about this, and I’ll set a trap.” Then the two friends went to a far corner of the room, out of all possible range of the door, and talked for a long time.