"But it's not possible," replied Greca, her head dropping dejectedly. "My people, as driven slaves, till the fields with great animals that were trapped in the surrounding jungles. They harness other great animals to haul burdens. But none of the beasts are like _this_ one. This kind cannot be tamed or harnessed. It is too ferocious. It is used only as a scourge of fear, to crush us into complete submission." "Can't be tamed?" Brand said. "We'll see about that! Come on, Dex." "Just a minute," said Dex. He flattened against the wall, motioning them to do the same. Then he leveled his tube at the door. Slowly, cautiously, the door began to swing back; and the Rogan that Dex had heard fumbling with the bolt stuck his huge head out to locate the escaped prisoners. Dex pressed the release coil of his tube. Without a sound, the Rogan slumped to the ground, a smoking cavity in its shoulders at the spot where its head had been set. In an instant the body, too, disappeared; an upward coiling wisp of black smoke marking its vanishing. Another Rogan, tiptoeing out, met the same fate; and another. And then the door was banged shut again, and the bolt ground into place on the inside. "That'll teach 'em to be careful how they try to rush us from _that_ door," said Dex, through set teeth. "Now let's see if that tank scheme of ours can be worked." * * * * * He picked up a tube dropped by one of the Rogans, and handed it to Brand; showing him which coil to press to get full force, as Greca had in turn informed him. "Down the field," commanded Brand. "We'll go about thirty yards apart, and try to herd this brute back through the walls of the dome building. Once it's inside, we'll try to rush to the lever before the Rogans can down us, and jam the thing past its terminal peg and into reverse action. I don't know that there _is_ a reverse to it--but we can try. "Greca dear,"--the girl started at the warmth of his thought, and a faint pink rose to her pale cheeks--"you'd better stay by my side. Your place as hostage-priestess of your people wouldn't save you if those devils catch you now. Besides, you can keep your tube leveled at the doorway as we go, and discourage any Rogans who might pluck up courage to try coming out again." They started down the field toward the nightmare thing that snarled and hissed in its corner. On one side of the big enclosure walked Brand, with Greca close beside him, glancing continuously over her shoulder at the rear door, and holding her tube in readiness to check any charge the Rogans might attempt to make from the tower building. On the other side, keeping an equal pace, advanced Dex.