Harry followed with his eyes and Dick was right. A long, thin
pole was rising, even as they looked on. Figures showed on the
roof of the tower. They were busy about the pole. It seemed to
grow longer as they watched. Then, suddenly, the dangling wires
they had first noticed were drawn taut, and they saw a cross-piece
on the long pole. And then, with a sudden rush of memory, Harry
understood.

"Oh! We have struck it!" he said. "I remember now - a portable,
collapsible wireless installation! I've wondered how they could
use wireless, knowing that someone would be sure to pick up the
signals and that the plant would be run down. But they have those
poles made in sections - they could hide the whole thing. It
takes very little time to set them up. This is simply a bigger
copy of what they use in the field. We've got to get out!"

He looked at his watch.

"Carefully, now," he said. "We've just about got time. That
sentry must be just about passing the place where we got over the
wall now. By the time we get there he'll be gone, and we can slip
out. We've got everything we came for, not that we've seen that!"

They started on the return journey through the woods. More than
ever there seemed to be danger about them. And suddenly it
reached out and gripped them - gripped Harry, at least. As he
took a step his foot sank through the ground, as it seemed. The
next moment he had all he could do to suppress a cry of agony as a
trap closed about his ankle, wrenching it, and throwing him down.