He was a small, gray man--gray suit, gray hair and close-cropped
mustache, and gray face, colorless and deeply lined. His age would be
hard to judge.

"The _Snowbird_; eh?" he observed, looking sharply from one to the other
of the five passengers of the huge flying machine. "_You_ are Amos
Henderson, sir?" he pursued, nodding to the professor. "I believe I have
heard your name before. Professor Henderson, whose scientific
discoveries have made us all marvel of late?"

"I am Professor Henderson," said the old gentleman, quietly. "And I
can vouch for my companions. These boys, my adopted sons, have built
this flying machine, and we are bound for Alaska."

"Indeed! Then I fear I have caused you some slight trouble, not to say
delay," said Mr. Ford. "We revenue agents are extremely anxious to
overhaul and interview all aviators along the border. You understand?"

"I believe that you have cause to suspect certain flying machines
operating between the Canadian towns and Maine settlements," admitted
Professor Henderson. "Quite right. And if our suspicions are based on
fact, innocent flying men like yourselves may well beware of the fellows
we are after. To be frank with you," pursued Mr. Ford, "a band of
desperate smugglers are operating by aid of one or more aeroplanes.
And piracy in the air may soon became as frequent--and as grave a peril
to innocent aviators--as was ever piracy on the Spanish Main."

"It seems impossible!" said the professor. "Who are these desperate
criminals?"