d Dr. Bird. "Good enough! I was afraid that you might
not have kept your gas mask on."

"My orders were to keep it on, sir," replied the lieutenant in muffled
tones through his mask, "but my mechanician did not obey orders. He
passed out cold without any warning about fifteen minutes ago."

"Where's your ship?"

"Right over here, sir."

"We'll take off at once. Your craft is equipped with a Bird
silencer?"

"Yes, sir."

"Come on, Carnes, we're going to follow that globe. Take the front
cockpit alone, Maynard; Carnes and I will get in the rear pit with the
spec and guide you. You can take of your gas mask at an elevation of a
thousand feet. You have pack 'chutes, haven't you?"

"In the rear pit, Doctor."

"Put one on, Carnes, and climb in. I've got to get this spec set up
before he gets too high."

The Douglass equipped with the Bird silencer, took the air noiselessly
and rapidly gained elevation under the urging of the pilot. Dr. Bird
clamped the gas-detecting spectroscope on the front of his cockpit and
peered through it.

"Southwest, at about a thousand more elevation," he directed.

"Right!" replied the pilot as he turned the nose of his plane in the
indicated direction and began to climb. For an hour and a half the
plane flew noiselessly through the night.

"Bald Mountain," said the pilot, pointing. "The Canadian Border is
only a few miles away."

"If they've crossed the Border, we're sunk," replied the doctor. "The
trail leads straight ahead."

* * * * *

For a few minutes they continued their flight toward the Canadian
Border and then Dr. Bird spoke.

"Swing south," he directed, "and drop a thousand feet and come back."

The pilot executed the maneuver and Dr. Bird peered over the edge of
the plane and directed the spectroscope toward the ground.

"Half a mile east," he said, "and drop another thousand. Carnes, get
ready to jump when I give the word."

"Oh, Lord!" groaned Carnes as he fumbled for the rip cord of his
parachute, "suppose this thing doesn't open?"

"They'll slide you between two barn doors for a coffin and bury you
that way," said Dr. Bird grimly. "You know your orders, Maynard?"

"Yes, sir. When you drop, I am to land at the nearest town--it will be
Lowell--and get in touch with the Commandant of the Portsmouth Navy
Yard if possible. If I get him, I am to tell him my location and wait
for the arrival of reenforcements. If I fail to get him o