Tom called Security 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!"