tead of the ass
you took him to be. He probably just pretended he was ignorant of
science. Why shouldn't he? That way he got a liberal education from
you in the very things he wanted to find out. Since you tied the can
to him he's had plenty of chances to build a duplicate of your control
apparatus--with the aid of some foreign government, no doubt--and now
they've stolen two of your machines to complete the job. Your secret
already is out and in the very hands you've tried to keep it from."

* * * * *

Shelton paled visibly as Eddie talked. "But--but how--" he stammered.

"How should I know how they did it?" the younger man countered.
"Here--let's take a look around. I'll bet they've left their trail
right here in this room."

He walked from one end of the laboratory to the other, peering into
corners and under work benches as he passed. Shelton trailed him like
a shadow, squinting through the square lenses of his spectacles.

They carefully avoided the partially invisible robot, for the humming
of its upper motors continued and clanking sounds occasionally issued
from the unseen upper portion. The enemies of David Shelton were still
at work on their hidden controls.

"Here--what's this?" Eddie exclaimed suddenly, pointing out a glinting
object in a dark corner of the laboratory.

Shelton examined it closely, looking over his shoulder. The object he
had located seemed to be a mounted and hooded lens, a highly polished
glass of about two inches diameter with its mounting attached rigidly
to the wall.

"Never saw that before," Shelton stated with conviction. "And--why--it
looks like an objective such as those used in the latest automatic
television transmitters."

"Just what it is," Eddie grunted. He picked up a pinch bar from a
nearby tool rack and drove its end through the glass as he spoke the
words.

A violent wrench tore the thing loose and broke away a section of the
thin plastered wall. There, in the cleverly concealed cavity behind,
was revealed the mechanism of the radio "eye." Somewhere, someone bad
been watching their every move. And abruptly the thrashings of the
robot ceased and its upper portion again became visible.

* * * * *

"Well," said David Shelton. "Well! Looks as if you're right, young
man. I'm astonished." His watery eyes looked sheepishly over the rims
of his glasses.

Lina watched their every move. She seemed to sense