hout interrupted him. He had seen something at the window: a
face pressed against the pane and contorted with unutterable malice.
Then it was gone. With the shout of warning still in his throat, Eddie
bounded through the door in pursuit of the intruder. Lina's cry of
recognition followed him into the twilight. "Carlos!" she had called.

He saw a stocky figure slink around the corner of the laboratory and
make for the underbrush beyond. In a flash he was after him. No, he
thought grimly, Shelton hadn't any enemy clever enough to duplicate
his transmitter! The hell he didn't! Who the devil was this fellow
Carlos anyway? He tore savagely at the impeding branches as he plunged
deeper and deeper into the thicket.

* * * * *

It was a fruitless chase and Eddie soon retraced his steps to the
laboratory. Swell mess he'd gotten himself into! His car was gone:
probably wrapped around a tree by this time. And here was a situation
that spelled real danger, a thing with which Shelton was utterly
unable to cope. As a matter of fact, he was so impractical--such a
visionary cuss, after the fashion of all geniuses--that he'd never be
convinced of the seriousness of the matter until it was too late. What
to do? The girl was a corker, though, and game as they made 'em. Just
the sort a fellow could tie to....

Lina's firm clear voice came to him through the open door of the
laboratory. "Dad," she was saying, "why don't you give it up? Let's go
back to New York where it is safe for you and for me. Let the things
go and forget about them. What do they amount to, after all? We've
plenty of money and you already have earned enough fame to last the
rest of your life. Come on now--please--for me."

"What do they amount to?" Shelton reiterated, his voice rising
querulously. "Lina, it's the most tremendous thing I've ever done.
Think for a moment of what my robots could accomplish in the next war.
And there'll be a next war as sure as you're alive. Think of it! No
sending of our young manhood into the bloody fields of battle; no
manning of our air fleets with the cream of our youth; no bloodshed on
our side whatsoever. Instead, these robots will fight the war. They'll
fight other robots too, no doubt, but the property of invisibility
will be an invincible weapon. It will be a war that will end war once
and for all. You can't--"

"Nonsense, Father," the girl returned sharply. "You've let your
enthusiasm run awa