is! On top of
that hill, do you see? We won't go much nearer. I don't want them to see
us, by any chance. All we need is to notice which way they're signalling."

They watched the house for some time before there was any sign of life. And
then it was only the flashes that they saw. Since the previous day some
sort of cover had been provided for the man who did the signalling.

"What do you make of it, Dick?" asked Harry eagerly, after the flashing had
continued for some moments.

"It looks to me as if they were flashing toward the north and a little
toward the west," said Dick, puzzled.

"That's the way it seems to me, too," agreed Harry. "That isn't what we
expected, either, is it?"

"Of course we can't be sure."

"No, but it certainly looks that way. Well, we can't make sure from here,
but we've got to do it somehow. I tell you what. We'll circle around and
get northwest of the house. Then we ought to be able to tell a good deal
better. And if we get far enough around, I don't believe they'll see us, or
pay any attention to us if they do."

So they mounted their machines again, and in a few moments were speeding
toward a new and better spot from which to spy on the house. But this, when
they reached it, only confirmed their first guess. The signals were much
more plainly visible here, and it was obvious now, as it had not been
before, that the screen they had noticed had been erected as much to
concentrate the flashes and make them more easily visible to a receiving
station as to conceal the operator. So they turned and figured a straight
line as well as they could from the spot where the flashes were made. Harry
had a map with him, and on this he marked, as well as he could, the
location of the house. Then he drew a line from it to the northwest.

"The next station must be on this line somewhere," he said. "We'll stick to
it. There's a road, you see, that we can follow that's almost straight. And
as soon as we come to a high building we ought to be able to see both
flashes--the ones that are being sent from that house and the answering
signals. Do you see?"

"Yes, that'll be fine!" said Dick. "Come on!"

"Not so fast!" said a harsh voice behind them. They spun around, and there,
grinning a little, but looking highly determined and dangerous, was the
same man they had seen the day before, and who had questioned them, when
the tire of their taxicab blew out! But now he was not in uniform, but in a
plain suit