your spunk, Reb," Grampa muttered.

"Speaking of children," Junior said, "where's Four?"

"Here." Four came through the airlock and trudged across the room, carrying a curious contraption made of tripod legs supporting a small box from which dangled a plumb bob. Behind Four, like a round, raspberry shadow, rolled Fweep.

"Fweep?" it queried hopefully.

"Not now," said Four.

"Where've you been?" Reba asked anxiously. "What've you been doing?"

"I've been all over Fweepland," Four said wearily, "trying to locate its center of gravity."

"Well?" Fred prompted.

"It shifts."

"That's impossible," said Junior.

"Not for Fweep," Four replied.

"What do you mean by that?" Joyce suspiciously asked.

"It shifted," Four explained patiently, "because Fweep kept following me."

"Fweep?" Junior repeated stupidly.

"Fweep?" Fweep said eagerly.

"He's why the flivver won't work. What Grampa invented was a linear polarizer. Fweep is a circular polarizer. He's what makes this planet so heavy. He's why we can't leave."

The land of the Fweep rotated once on its axis, and Grampa lowered the nippled bottle from his lips. He sighed. "I got it figured out, Four," he said, holding out the pircuit proudly. "A missionary takes over a non-rowing type cannibal, leaves him there, and then the rowing cannibal takes over the other cannibal and leaves him there and—"

"Not now, Grampa," Four said inattentively as he watched Fweep making the grand tour of the cabin.

The raspberry sphere swept over a scattering of crumbs, engulfed them, absorbed them. Four looked at Joyce. Joyce was watching Fweep, too.

"Rat poison?" Four asked.

Joyce started guiltily. "How did you know?"

"There's no use trying to poison Fweep," Four said calmly. "He's got no enzymes to act on, no nervous system to paralyze. He doesn't even use what he 'eats' on a molecular level at all."

"What level does he use?" Junior wanted to know.

"Point the scintillation counter at him."

Junior dug one of the counters out of the supply cabinet and aimed the pickup at Fweep. The counter began to hum. As Fweep approached, the hum rose in pitch. As it passed, the hum dropped.

Junior looked at the counter's dial. "He's radioactive, all right. Not much, but enough. But where does he get the radioactive material?"

"He uses ordinary matter," Four said. "He must have used up the few deposits of natural radioactives a long time ago."

"He uses ordinary substances on an atomic level?" Junior said unbelievingly.

Four nodded. "And that 'skin' of his—whatever it is he uses for skin—is more efficient in stopping particle emissions than several feet of lead."

Fred studied Fweep thoughtfully. "Maybe we could feed him enough enriched uranium from the pile to put him over the critical mass."

"And blow him up? I don't think it's possible, but even if it were, it might be a trifle more than disastrous for us." Four giggled at the thought.

Joyce glared at him furiously. "Four! Act your age! We've got to do something with him. It's preposterous that we should be detained here at the whim of a mere blob!"

"I don't figure it's a whim," Grampa said. "Circular gravity is what he's got to have for one reason or another, so he just naturally bends the space-time continuum around him—conscious or subconscious, I don't know. But protoplasm is always more efficient than machines, so the flivver won't move."

"I don't care why that thing does it," Joyce said icily. "I want it stopped, and the sooner the better. If it won't turn the gravity off, we'll just have to do away with it."

"How?" asked Four. "Fweep's skin is pretty close to impervious and you can't shoot him, stab him or poison him. He doesn't breathe, so you can't drown or strangle him. You can't imprison him; he 'eats' everything. And violence might be more dangerous to us than to him. Right now, Fweep is