"Damn!" he cried as he received negative answers. "The current wasn't strong enough. It's going to get away." Carnes jerked his automatic from under his armpit and poured a stream of bullets into the fleeing monster. Slower and slower the motion of the creature became, and its movements again became jerky and convulsive. "Keep it in sight!" cried the doctor. "We may get it yet!" Cautiously the three men followed the retreating horror, Leffingwell pushing before him the platform holding the ultra-violet ray apparatus. The chase led them over familiar ground. "There is the crack!" cried the lieutenant. "Too late!" replied the doctor. He rushed forward and seized the lower limb of the monster and tried with all his strength to arrest its flight, but despite all that he could do it slid sideways through the crack in the wall and disappeared. A final backward kick of its leg threw the doctor twenty feet against the far wall of the cave. "Are you hurt, Doctor?" cried Carnes. "No, I'm all right. Put on your masks and start the gas! Quick! That may stop it before it gets in far!" * * * * * The three adjusted gas masks and thrust the mouths of two gas cylinders which were on the light truck into the crack, and opened the valves. The hissing of the gas was accompanied by a thrashing, writhing sound from the bowels of the earth for a few minutes, but the sound retreated and finally died away into an utter silence. "And that's that!" cried the doctor half an hour later as they took off their gas masks outside the cave. "It got away from us. Carnes, how soon can we get a train back to Washington?" "What kind of a report are you going to make to the Bureau, Doctor?" asked Carnes as they sat in the smoker of a southern train, headed for the capital. "I'm not going to put in any report, Carnes," replied the doctor. "I haven't got the creature or any part of it to show, and no one would believe me. I am going to maintain a discreet silence about the whole matter." "But you have your photograph to show, Doctor, and you have my evidence and Lieutenant Leffingwell's." "The photograph might have been faked and I might have doped both of you. In any case, your words are no better than mine. No, indeed, Carnes, when I failed to make the current strong enough to kill it outright I made the first of the moves which bind me to silence, although I thought that two hundred thousand volts would be enough.