as soon as there were any important developments.

And so Paul and Arthur slipped out to the garage, which was a favorite
hiding place. Now it was especially safe, since Marcel, the chauffeur,
had gone to Brussels with their uncle, and there was no likelihood of
any unwelcome interruptions. They repaired, therefore, to the room
above the one in which their uncle's automobile was kept, and spread
out the papers they had captured from the German spy. First there was
the sketch they had already seen of the Boncelles fort; then, equally
detailed, they found sketches and maps of the other forts--Flemalle,
Embourg, Chaudfontaine, Fleron, Evegnee, Pontisse, Liers, Lanlin,
Longin and Hollogne--the great chain of detached forts that made Liege,
in the opinion of military engineers, one of the strongest fortified
towns in Europe.

These forts were not immediately in the town; they were about five
miles, on an average, from the old citadel, long since disused as a
place for actual fighting. The connections between the various forts,
intended, as both boys knew, for the greater facility of their defence
by means of troops fighting more or less independently, were carefully
traced on another map, in which the contour of the land and the natural
shelter were shown. And on this map, at certain spots, there were
strange marks--well beyond the perimeter of the forts themselves, that
is, outside the line that might be drawn around Liege and passing
through each of the forts.

"Look at those crosses," said Paul. "What do you suppose they mean,
Arthur?"

"I don't know," said Arthur, frowning. "But we can find out, you know."

"You mean by going to one or two of these places? They're some
distance off."

"But we ought to find out--don't you think so?"

"Yes, you're right, of course. We can find them easily enough."

"Yes. All we've got to do is to take the map along with us. Then when
we get near we can make sure by looking at it."

"We could do that, but I think we won't, Arthur. Suppose we ran into
the man it belongs to again? We might not get away from him another
time, and I think it would be just as well to leave these maps here.
We can hide them, and then write a note and leave it where it will be
found in the morning, telling them where we hid the maps."

"What's the use of hiding them if we tell some one where they are,
Paul?"

"Can't you see? Suppose something happens to us, so that we can't get
back?