screamed. Tharp's face reddened. "You won't get far," he threatened. "I'll pay this duchal in a few minutes; they'll let me free and I'll—" "You don't realize," Farrell interrupted, "Martians are sickly, sensitive people and they're adept at projecting sensations of agony from their brains. On the other hand, Earthmen are strong physically and know nothing about projecting physical or mental pain—" He paused to watch three Martians who removed gleaming, sharp knives from their tunics. They pressed the blades against Tharp's arms. The knives cut through his coat, shirt and flesh. The cloth reddened quickly. "They want their duchal payment," Farrell informed him. "They'll get it if they have to slice you to ribbons." Tharp's wild eyes stared at the dial before him. The needle touched the second graduation, then settled to the "0" position. "You see," Farrell continued, "it's a matter of equivalent. Earthmen are so strong, they have to really suffer physically before they can match a duchal payment that a Martian can create as easy as snapping his fingers!" Once more, the glittering knives bit into Tharp's flesh. He screamed with pain. "Get help! Get help before they kill me!" Farrell went for help. But, once beyond the thick door that suddenly suffocated Tharp's shrill screams of pain, he didn't run for help. He walked slowly.