A crazy idea had come into the Earthman's mind. He did not expect his plan to work but it was all he could do. With an air of one resigned to his fate, he obeyed the order. He felt the Martian fumbling with the manacles. He was evidently using only one hand. The other presumably still held the automatic leveled at Shelby's back. But it was useless to think of such things. A slim finger touched the young engineer's wrist. He caught it, twisted it back at the same time, then, summoning all the quickness and force he could muster, he ducked low and hurled himself backward straight into the Martian. There was a loud report. A hot pain seared into the fleshy folds beneath Austin's left shoulder blade. Those hidden in the darkness at the farther end of the room did not dare to fire for fear of injuring their master. Now Shelby was grappling with Hekalu. He gripped the hand that held the automatic. Two more reports--ineffective, and then the two fell clawing and in a heap on the floor. The shaded lamp was upset and its illumination globes were broken. There was darkness. Shelby heard the shuffle of running feet coming across the marble pavement of the chamber. Help for Hekalu! He'd have to hurry. But the Martian noble, racially much frailer than the people of Earth, was no match for the athletic Shelby. In a moment he was pinned, unable to move. The Earthman tore his weapon from him and thrust its muzzle against his recent opponent's chest. Before he fired he saw the Martian's bold smile; whatever failings Hekalu Selba had, cowardice was not among them. On the heels of the gun's report Shelby darted from the room and down the short hallway which led back to the central light-well of the Selba establishment. If he could only somehow reach his plane! He gripped the doorknob and shoved fiercely, but the stout metal panels were immovable. He might have known that the outer door would be locked! Oh, what an unutterable ass he had been! Now what? A hoarse cry of triumph caused him to turn. Alka was racing toward him with leveled pistol. A spray of projectiles spread toward Shelby but the slave's aim was bad and none of them took effect. A split second later Alka pitched to the floor with a bullet through his brain. * * * * * But there was another to be reckoned with--one who waddled along rapidly on short powerful legs. Its arms were long and black and more powerfully muscled than a gorilla's. One hand brandished a metal knob-stick, and the other, a long-barreled pistol of Martian design. Silvery armor set with jewels that glittered wickedly in the dim light of the hallway crossed the creature's breast. Its head was bulbous, and its face, set deep in plates of shining black chitin-like armor, consisted only of two enormous eyes and a lipless mouth. No nose at all! The horror Shelby had seen on the liner!