"I wish something would happen," muttered the lieutenant. "This is getting on my nerves. "Something is about to happen," replied Dr. Bird grimly. "Listen to that steer." * * * * * The bellowing of the steer had suddenly increased in volume and, added to the note of discontent, was a note of fright which had previously been absent. Dr. Bird bent over his ultra-violet search-light and made some adjustments. He handed a helmetlike arrangement to each of his companions and slipped one on over his head. "I can't see a thing, Doctor," said Carnes in a muffled voice. "The objects at which you are looking absorb rather than reflect ultra-violet light," said the doctor. "This is a sort of a fluoroscope arrangement, and it isn't perfect at all. However, when the monster comes along, I am pretty sure that you will be able to see it. You may see a little more as your eyes get accustomed to it." "I can see very dimly," announced the lieutenant in a moment. Dimly the walls of the cave and the platform before them began to take vague shape. The three stared intently down the beam of ultra-violet light which the doctor directed down the passageway leading deeper into the cave. "Good Lord!" ejaculated Carnes suddenly. Slowly into the field of vision came the hideous figure they had seen on the film. As it moved forward a rustling, slithering sound could be heard, even over the bellowing of the steer and the hum of the apparatus. The odor of musk became evident. Along the floor toward them the thing slid. Presently it reared up on its hind legs and its enormous bulk became evident. It turned somewhat sideways and the correctness of Dr. Bird's hypothesis as to its peculiar shape was proved. All of the bulk of the creature was in two dimensions. Forward it moved, and the horrible human hands stretched forward, while the mouth split in a wide, toothless grin. Nearer the doomed steer the creature approached, and then the reaching hands closed on the animal. There was a blinding flash, and the monster was hurled backward as though struck by a thunderbolt, while a horrible smell of musk and burned flesh filled the air. "After it! Quick!" cried the doctor as he sprang forward. * * * * * Before he could reach the prostrate creature it moved and then, slowly at first, but with rapidly gaining speed, it slithered over the floor in retreat. Dr. Bird's hand swung through an arc, and there was a deafening crash as a hand-grenade exploded on the back of the fleeing monster. An unearthly scream came from the creature, and its motion changed from a steady forward glide to a series of convulsive jerks. Leffingwell and Carnes threw grenades, but they went wide of their mark, and the monster began to again increase its speed. Another volley of grenades was thrown and one hit scored, which slowed the monster somewhat but did not arrest the steady forward movement. "Any more bombs?" demanded the doctor.