y, that's what
they use for S.O.S. at sea! It's criminal. Endangers every ship in
distress. Five years in prison for it. Get him, can't you?"

"Can't. That's the trouble. Every time I think I've got him spotted he
seems to move."

"To move!"

"Yes, sir."

"That's queer! I'll be up right away."

"Come on," exclaimed Curlie, grabbing his hat and dragging Joe to his
feet. "It's a big one. Moves, he says. Sends 600; big power. Bet it's
that same hotel fellow. Gee whiz! Supposing it turned out to be that
sixteenth story girl and she caught me spying on her. I tell you it's
something big!"

Impatient at the slowness of the up-shooting elevator, Curlie at last
leaped out before the iron door at the top was half open, then two
steps at a time sprang up a flight of stairs. Out of breath, he arrived
at the final landing, sprang through the door to the secret tower room,
then seizing his headpiece, sank into a chair.

By a single move of the hand, Coles Masters indicated the radio-compass
he had been listening in on.

"That's where he was, last time he spoke," he grumbled, "but no telling
where he'll be next. He's been dodging all over that stretch of
country."

Curlie's fingers moved rapidly. He adjusted the coil of a radio-compass
here, another there and still another here. He twisted the knob of each
to the 600 mark, then, twisting the tuning knobs, lined them all up to
receive on the same wave length. The winding of each was set at a
slightly different angle from any other.

"That about covers him," he mumbled. "Get the distance?"

"Near as I could make out," said Coles Masters, "it was from ten to
fifteen miles. He moves toward us, then away at times, just as he does
to right and left."

"Hm," sighed Curlie, resting his chin on his hands. "That's a new dodge,
this moving business. Complicates things, that does."

For a time he sat in a brown study. At last he spoke again, this time
quite as much to himself as to the other:

"Folks don't move unless they have a way to move. That fellow has some
means of locomotion. Anyway," he sighed, "it's not our friend of the big
hotel unless--unless he or she or whoever it is has taken to locomotion,
and that's not likely. Not the same side of the city. Out near the
forest preserve."

"Yes, or a little beyond," said Coles.

"What do you think," asked Curlie suddenly, "has he got an automobile or
an airplane?"

"Can't tell," said Coles thoughtfully. "You can't really