Only Harkness and Chet were the builders. Diane's strength was not equal to the task of cutting tough wood with a crude stone ax, and Herr Kreiss, though willing enough to help when asked, was usually in his own cave, busied with mysterious experiments of which he would tell nothing. Towahg, their only remaining Helper, could not be held. Too wild for restraint of any kind, he would vanish into the jungle at break of day to reappear now and then as silently as a black shadow. But he kept them all supplied with game and fruit and succulent roots which his wilder brethren of the forest must have shown him were fit for food. And then came an interruption that checked the work on the house, that drained the brilliant sunshine of its warmth and light, and turned all thoughts to the question of defense. The two had been working on the roof, while Diane had returned to the jungle for another of the big leaves. She carried her bow on such trips, although the weeks had brought them a sense of security. But for Chet this feeling of safety vanished in the instant that he heard Harkness' half-uttered exclamation and saw him drop quickly to the ground. * * * * * Beyond him, coming through the green smother of grass that was now as high as her waist, was Diane. Even at a distance Chet could see the unnatural paleness of her face; she was running fast, coming along the trail they had all helped to make. Chet hit the ground on all fours and reached for the long bow with which he had become so expert; then followed Harkness who was racing to meet the girl. "An ape!" she was saying between choking breaths when Chet reached them. "An ape-man!" She was clinging to Harkness in utter fright that was unlike the Diane he had known. "Towahg," Harkness suggested; "you saw Towahg!" But the girl shook her head. She was recovering something of her normal poise; her breath came more evenly. "No! It was not Towahg. I saw it. I was hidden under the big leaves. It was an ape-man. He came swinging along through the branches of the trees: he was up high and he looked in all directions. I ran. I think he did not see me. "And now," she confessed, "I am ashamed. I thought I had forgotten the horror of that experience, but this brought it all back.... There! I am all right now." Harkness held her tenderly close. "Frightened," he reassured her, "and no wonder! That night on the pyramid left its mark on us all. Now, come; come quietly." He was leading the girl toward the knoll that they all called home. Chet followed, casting frequent glances toward the trees. They had covered half the distance to the barricade when Chet spoke in a voice that was half a whisper in its hushed tenseness. "Drop--quick!" he ordered. "Get into the grass. It's coming. Now let's see what it is." * * * * *