Chick went to the filing cabinets devoted to storage of accepted design tracings, hunted through a folder, kept under lock and key, and put the tracing on the table.

An exclamation caused them all to turn.

The control room operator was staring, astonished and pleased: he leaped to his feet.

“So that’s what you found!” he exclaimed, moving quickly forward. “Brigantine-nothing! That’s a sketch I—er—mislaid. I guess it got mixed up with the regular stuff and was brought in here—but how did it get to the swamps?” Chick watched him with narrowed eyes.

“A sketch,” Chick thought. “Oh, yes! Part of it in faded ink and part of it in India waterproof ink, the sort they use here!”

He did not voice his suspicion. It came to his mind that the control room man would bear watching. Through him, Chick decided, they might get some clue to the mysteries they had encountered.

“Before I touch it,” the man continued, “Mr. McLeod, just take a look at the lower, left-hand corner and see if my initials are put in the angle of what is meant to be the bow of a new-shaped fuselage.”

“Yes,” admitted the airport manager, with a glance at the sketch. “J. V.—John Vance. Take it, and let’s get out of here so the boys can go to work. They’ll be paid by the aircraft company, and it’s a good thing. They’ll be paid! If any more trouble comes to our airport, I guess Doc, and Scott, won’t draw any pay checks.”

Scott, coming in from the adjoining office, laughed.

“I’ll ‘haunt you’ if I don’t!” he chuckled.