In those horrible seconds, there was nothing Carter could think of to do but fling himself and the girl flat on the ground, squeezing into an opening which a moment ago would have been too small for them. Vaguely he was aware of the sound of the monster's claws as they scratched on the rocks. It came with a rush. It was a monster thirty or forty feet long in a moment. Carter had a dim vision of the broad under surface of the tremendous body as it scrambled almost directly over him--scuttling headlong over the clump of rocks among which its dwindling prey were crouching. "Now, Lea--up! Run!" They staggered over the swaying, outward-crawling ground. In a moment Carter turned to look back. Far behind them in the glowing darkness, the insect again had reared up, vainly searching for them--a titan thing now, its reddish body looming a hundred feet or more above the ground. For a second or two it showed etched against the blur of sky, its eyes glaring like distant lighthouse lamps. Then an expanding cluster of nearby rocks intervened and they could no longer see it. "We've got to be careful, Lea. Do things quickly or we'll get lost in size." With the attacking monster gone, Carter's wits came back to make him aware of a new danger. They had not intended to take this double dose of the diminishing drug. Gripping the girl, Carter stood unsteadily, peering around at the swaying scene. The apparent enlarging of the landscape was greatly accelerated, so swift that it was dizzying. But he could still recognize the main familiar features. Here was the rift into which they had determined they must go.... * * * * * The doubled drug, though accelerated in action, seemed to last no longer than a smaller dose. But it was two hours or more of wild scrambling. Then at last Carter was aware by the visible slowing of the expanding scenes, that again it was wearing off. "Well, thank God for that, Lea," he murmured. "Don't let's try anything like that again." They were resting, preparing to take more of the drug, when on the bottom of Lea's ragged short shirt Carter saw a tiny ant crawling, evidently disturbed by the movement. He stared; then he reached, squashed it between thumb and forefinger. "Just an ant," he said. "But those red ones can bite. You must have gotten it on you in the garden when we left." A sudden thought made his jaw drop. A red ant--an eighth of an inch long maybe--six legs--a body pinched in the middle.... "Why, good Lord, Lea," he gasped. "There could have been more red ants on us. One of them dropped off while we were getting small--then while we slept it found us and attacked us! That was the monster that nearly got us!" Just an ant! What an amazing difference size could make! Surely they still had much to learn about this weird traveling! Carter could see that the cliffs here were honeycombed with tunnel-passages and cave-mouths. After resting a while they took more of the drug and went on.