heir 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.

Safe in the sanctuary of this altar dedicated to some deity that they
could never imagine, they crouched close to its blood-clotted surface,
and stil