rity and asked Harlan Ames to come over to the laboratory
at once. The security chief arrived within moments. Quickly Tom filled
him in on the details of the puzzling telephone call.

"Think back, skipper," Ames urged. "Was there anything at all you can
remember about the voice that might give us a tip-off? I mean, was it
deep, or maybe a bit higher-pitched than you expected? Or anything about
the way the caller pronounced his words?"

Tom shook his head. "Nothing. That's the trouble. He spoke only a couple
of sentences, but so far as I knew, it _was_ my father calling!"

"Hmmm." Ames frowned. "What about background noises?"

Tom thought hard. "None. If I had detected any special sounds during the
call, I'm sure they would have stuck in my mind."

Ames tried another tack. He asked how many people had known about the
expected arrival of the brain energy from space. This was harder to
answer, but as Tom and his father enumerated the persons, it did help to
narrow the circle of suspects.

Besides the Swifts, Chow, Phyl, Ames, and George Dilling, there were
three groups who had had access to the information. One was the radio
operators at the space-communications laboratory. Another consisted of
Arv Hanson and Hank Sterling and the workmen who had taken part in
building the energy container. The last group, which also included Hank
and Arv, were the technicians who had actually gone to the hillside to
await the visitor from Planet X.

Tom scowled. "None of those people would pull such a trick, Harlan--any
more than the ones like you and Arv and Hank who are above suspicion.
Most of them could have easily obtained the news without going through
such a rigmarole."

Mr. Swift nodded. "Tom's right. Unless, of course, they had some urgent
reason for wanting to find out as soon as possible."

"Which makes me think it may have been an outsider after all," Tom
argued. "Remember, the Brungarians may have intercepted the code
messages to or from our space friends." After a moment's silence, he
added gloomily, "Whoever the caller was, he knew the energy was
arriving. And now he knows it's here!"

Bud interjected, "Well, if he was a Brungarian agent and he's hoping to
steal the brain energy, one thing's sure. No earthquake will demolish
this place as long as the energy is here at Enterprises."

"A comforting thought, Bud," Mr. Swift commented with a wry smile.

Again Tom frowned. "At any rate, Harlan, see if you can get a