might be held.

But to do this would be in direct violation of their orders, and they
dared not take any risks. For to do so might involve not only themselves
in danger, but others as well. And that view of the matter determined
them. They would have to await their opportunity for rescuing their
chum--if it could be accomplished.

Their tour of duty aloft that day was without incident. This is not an
usual condition at times along the long battle front. Men can not go on
fighting without stop, and there come lulls in even the fiercest battle.
Flesh and blood can stand only a certain amount of torture, and then
even the soul rebels.

So Tom and Jack drifted peacefully down to their aerodrome, noting that
it was being newly camouflaged, for the recent rain had played havoc
with some of the concealments.

As far as possible both the Germans and the Allies tried to conceal the
location of their flying camps. The aeroplanes and balloons needed large
buildings to house them, and such structures made excellent and, of
course, fair war-marks for bombing parties in aeroplanes hovering aloft.
So it was the custom to put up trees and bushes or to stretch canvas
over the aerodromes and paint it to resemble woods and fields in an
effort to conceal, or camouflage, the depots where the airships were
stationed. But this work was done by a special detail of men, and with
it Tom and Jack had nothing to do.

They turned their machines over to the mechanics, who would go carefully
over them and have the craft in readiness for the next flight. Then,
being free for several hours, the two young airmen could do as they
pleased, within certain limits.

"Well, did anything occur to you?" asked Jack, as he and Tom, having
divested themselves of their heavy fur-lined garments, went to the mess
hall, which was in an old stable, from which the horses had long since
been removed.

"You mean a plan to rescue Harry?"

"That's it."

"No, I'm sorry to say I can't think of a thing," Tom answered. "I
thought I would, but I didn't. Have you anything to say?"

"Yes. Let's go to Paris."

"You mean to see--er--?"

"Yes!" interrupted Jack with a smile. "This is their day off, and we
might as well have a little enjoyment when we can. From the easy time we
had to-day we'll have some hard fighting to-morrow. This was too good to
last. Heinie is up to some mischief, I think."

"Same here."

So, having received permission, they went to Paris, and