danger," agreed Chester. "All we have to do is to
stay within our own lines."

Half an hour later found them speeding southward, well in the rear of the
great battle line. Hal himself was at the wheel and Chester sat in the
tonneau of the machine. Through Ypres, Douai and many smaller towns the
huge car sped without a stop. At Roy they halted for a fresh supply of
petrol, and immediately resumed their journey.

But the lads were not entirely familiar with the lay of the land, and
this fact resulted in throwing them into great danger once more.

Just south of Roy the long battle line--which had previously stretched
straight southward--swerved suddenly to the east. The lads turned with
it all right, but too soon. Instead of going straight south to the
banks of the river Aisne, as they should have done, they turned
eastward some distance north of this river, and were in trouble before
they realized it.

Neither lad thought anything of the fact that they were pushing straight
through the mass of French troops in this region, and it was not until
they had come into an isolated region--an opening between the two great
armies--that Chester surmised there was something wrong. The desolate
appearance of the land spelled suspicion to him, and, leaning forward in
his seat, he shouted to Hal:

"Slow down, quick!"

Hal obeyed without question and then turned to his chum to ascertain the
reason for this abrupt command.

"We must have gone clear through our own lines," Chester explained. "If
we hadn't, certainly there would be troops about. I believe we must be
right between the two armies."

"I don't think so," replied Hal. "There are probably more French troops
ahead of us."

"I am sure I'm right," persisted Chester.

"Well, it's not worth while taking a chance," said Hal. "We'll turn
south here."

At a cross road he swerved toward the south again. But, although neither
lad realized it then, they had penetrated right through the German lines
where they had been thinnest and most greatly scattered. They were still
north of the Aisne, and the main German line lay between them and the far
shore, where the French were massed in strength. They could have turned
west again at this point and probably have reached safety by the way they
had come; but neither realized his danger, and so the big car sped south
directly toward the enemy.

It was night now, and the machine was forced to travel more slowly,
running along at a sn