"Not necessarily...."
"Bah! What other kind of intelligent life is there?"
"I don't know. But before we speculate too much, let's look at the
tri-di. The camera may have caught something I missed."
It hadn't. The three-dimensional pictures added nothing.
"It probably was operated either by programmed automatics or by remote
control," Hilton decided, finally. "But how did they drain all our
power? And just as bad, what and how is that other point source of power
we're heading for now?"
"What's wrong with it?" Sawtelle asked.
"Its strength. No matter what distance or reactant I assume, nothing we
know will fit. Neither fission nor fusion will do it. It has to be
practically total conversion!"