st then another thing came to pass that caused Jack's heart to feel as
though a cold hand had been pressed down on it. From above came a
familiar sound, especially to the ear of an aviator. It was the
unmistakable buzz of an airplane motor. The sound was growing constantly
louder, as though the machine were heading directly toward the chateau.

Of course it was next to impossible for it to be an allied plane; and so
Jack must conclude that it bore some courier sent from Hindenburg's
headquarters, wherever they might be, with a message of vast importance
meant for the general commanding the sector opposing the American
advance. Tom and Jack exchanged looks. It seemed as though they were now
between the upper and the nether millstones. If they lingered where they
were the soldiers were almost certain to come upon them; and should they
choose to start their motor and make a successful start into the upper
air currents the hostile plane would be ready to challenge them to
deadly combat.

But Tom was already beginning to fasten little Helene in a seat
alongside his own position. From this Jack understood that his chum's
mind was made up, and that half a dozen waiting planes might not daunt
him. They would have to take chances one way or another; and by going
aloft they might at least be in a position to hold their own.

Jack hoped with all his heart they could get away without an upset. The
ground was far from being all that might be wished; but then he had
known even worse in his experience, and had never yet come a cropper.
Besides, Tom would be at the helm, and that stood for a great deal. Jack
hastened to get aboard.

None too soon did the pilot get his machine to going. The Huns were
already howling close by, and must have turned in at the cemetery
entrance as though suspecting the truth.

With a whirr and a clatter the plane was off. Guns had commenced to bark
and red splashes of fire to stab the opaque mist that had now fallen on
the lower ground with the deepening night. Jack felt like laughing at
all these vain efforts to stop their departure.

Bumping along, Tom increased the speed, with Jack waiting in more or
less suspense to ascertain what the outcome would be. Ahead of them rose
the barrier of trees. If they struck that all was lost. But Tom was on
the alert, and just in good time he changed his lifting lever that
caused the nose of the plane to incline upward.

With a rush and a roar they cleared the tr