Greg whistled soundlessly through suddenly bared teeth.
"That takes power," he said, "and I'm afraid Craven has it. Power to burn."
"The collector field?" asked Russ.
Greg nodded. "A field that sucks in radiant energy. Free energy that he just reaches out and grabs. And it doesn't depend on the Sun alone. It probably makes use of every type of radiation in all of space."
Russ slumped in his chair, smoking, his forehead wrinkled in thought.
"If that's what he's got," he finally declared, "he's going to be hard to crack. He can suck in any radiant vibration form, any space vibration. He can shift them around, break them down and build them up. He can discharge them, direct them. He's got a vibration plant that's the handiest little war machine that ever existed."
Greg suddenly wheeled and walked to a wall cabinet. From it he took a box and, opening it, lifted out a tiny mechanism.
He chuckled deep in his throat. "The mechanical shadow. The little machine that always tells us where Craven is—as long as he's wearing his glasses."
"He always wears them," said Russ crisply. "He's blind as a bat without them."
Greg set the machine down on the table. "When we find Craven, we'll find the contraption that's blanketing Jupiter and its moons."