danger.

But if the danger was great, Greene was a master of his craft. He
swooped downward. Then, when he was scarcely a hundred feet up, he
caught the machine with a fine show of skill and held it, for a moment,
on an even keel.

"We'll chance it in the next field," he called. "Can't stay up any
further. Here goes!"

Down, down, they went. Then they were down, bumping along. But the
element of luck that, despite all his skill, Greene had to have, favored
him. The field was smooth and the monoplane came to rest safely. In an
instant both were out, Greene first, since Frank, having to free himself
from his straps, was delayed.

"Quick! The small flashlight!" called the flyer. "Here, give it to me!
If we're to save any essence we've got to be quick!"

He took the light. But a quick look over the tank failed to show a
spurting stream of gasoline.

"By Jove! Wonder if I could have been mistaken? Perhaps it was something
else they hit!" cried Greene. But then he groaned. As he unscrewed the
cap of the tank and peered in, he saw that it was bone dry.

CHAPTER XIII

A DANGEROUS ERRAND

For a moment Greene was speechless with despair. Fate had tricked him,
it seemed, after he had done his best--and a better best than most men
could even have attempted. Then he grinned.

"We'll have to hoof it," he said. "A good twelve miles, too! If we were
champions at cross-country work it would take us the best part of two
hours. And it's so long since I've used my legs that I don't know how
long I'll be."

"There's one chance," said Frank. "I remember that I saw a little inn on
the road the Germans took this afternoon. We're not so very far from
that now. These little inns along the roads in France all have petrol
for motorists who run short. If I went there I might get some."

Greene shook his head doubtfully.

"The government's taken all the essence it could find," he said, "I
don't believe they'd have any. And, besides, there's a good chance that
the Germans have men there."

"Still it's a chance," said Frank. "Won't you let me try? If I can't get
it we shan't lose much time. And if I do, look at the difference it
would make."

"That's true enough," said Greene. "All right, try it. I'll mend up the
hole, when I find it, and if you do get some essence, we can be off at
once. Good luck!"

Frank was on his way already, slipping away in the direction whence they
had come. Luckily enough, he got his bearings by