A prolific race, indeed, Chet thought, and this human automaton down there was leaving the women to produce more victims; leaving the children till they were fully grown, taking only the best and strongest of the pack--for what? His question was answered in part in the next instant. While the wailing cry quivered again upon the air, the chosen hundred took up their somnambulistic walk. The messenger from the pyramid came after like a herdsman driving cattle to the slaughter. They passed from Chet's view as they rounded the rear of the pyramid, and then he heard the scuff and clatter of their ascent. No need to explain to the others; each of the four saw all too clearly their predicament. From the rear, coming steadily on, was the savage throng; before them, plainly visible from below, was the lighted edge where the altar rock stood. To step out there in full view would bring the whole pack upon them; to drop down to another level would expose them as plainly. Only in the dark shelter of the projecting capstone were they hidden from the upturned faces now massed solidly about. Their problem was solved for them by the sight of a savage body, black, ragged with unkempt tufts of hair--another!--a score of them! They were rounding the corner of the pyramid and walking stiffly toward them, pressing upon them. And the arrow on the drawn bow in Chet's hand was never loosed, for each savage face was wide-eyed and devoid of expression; the ape-men neither saw nor felt them. They were hypnotized, as Chet was suddenly aware; they knew only that they must follow the mental instructions that were guiding them on. The black, animal bodies were upon them. Chet came from the stupefying wonder that had claimed them all and sprang to shield the group from the steady advance. Harkness was beside him, and an instant later, Kreiss; Diane was at their backs. And the weight of the advancing bodies swept them irresistibly backward, out into the light, along the wide step toward the passage that yawned darkly under the projecting cap. * * * * * There was no checking the avalanche of bodies--no resisting them: the men were carried along; it was all they could do to keep their footing. Harkness sprang backward to take Diane in his arms and retreat with her before the advancing horde. Chet was waiting for an outcry from below, for some indication that despite the mass of bodies that smothered them, their presence had been observed. But only the wailing cry persisted. There was another advancing column that had circled the other side, and now both groups were meeting at the passageway. Chet gripped at the figure of Kreiss who was being swept helpless toward the dark vault and he dragged him back. The two fought their way out toward the front and saw Harkness doing the same. "The altar," gasped Chet; "up on the altar!" And he saw Harkness swing Diane up on the stone, then turn and extend a helping hand toward the two men.