It seemed probable that any attempt to take over a human mind would disturb something. There had to be a point of interaction, somewhere.

That was what the Attison Detector was supposed to detect. Maybe it would.

The spaceships, three men to a ship, dotted space between Earth and Mars, forming a gigantic sphere with Earth in the center.

Tens of thousands of men crouched behind gunfire panels, watching the dials on the Attison Detector.

The unmoving dials.

"Do you think I could fire a couple of bursts?" Edwardson asked, his fingers on the gunfire button. "Just to limber the guns?"

"Those guns don't need limbering," Cassel said, stroking his beard. "Besides, you'd throw the whole fleet into a panic."

"Cassel," Morse said, very quietly. "Get your hand off your beard."

"Why should I?" Cassel asked.

"Because," Morse answered, almost in a whisper, "I am about to ram it right down your fat throat."

Cassel grinned and tightened his fists. "Pleasure," he said. "I'm tired of looking at that scar of yours." He stood up.

"Cut it," Edwardson said wearily. "Watch the birdie."

"No reason to, really," Morse said, leaning back. "There's an alarm bell attached." But he looked at the dial.

"What if the bell doesn't work?" Edwardson asked. "What if the dial is jammed? How would you like something cold slithering into your mind?"

"The dial'll work," Cassel said. His eyes shifted from Edwardson's face to the motionless indicator.

"I think I'll sack in," Edwardson said.

"Stick around," Cassel said. "Play you some gin."

"All right." Edwardson found and shuffled the greasy cards, while Morse took a turn glaring at the dial.