?" exclaimed Ennis. "I don't see anyone."

"We'll soon find out," the inspector said. "Sturt, run close to the
ledge there and we'll get out on it."

Sturt obeyed, and as the cutter bumped the ledge, Campbell and Ennis
leaped out onto it. They looked this way and that along it, but no one
was in sight. The weirdness of it was unnerving, the strangely lit,
mighty cavern, the assembled boats, the utter silence.

"Follow me," Campbell said in a low voice. "They must all be somewhere
near."

He and Ennis walked a few steps along the ledge, when the American
stopped. "Campbell, listen!" he whispered.

Dimly there whispered to them, as though from a distance and through
great walls, a swelling sound of chanting. As they listened, hearts
beating rapidly, a square of the rock wall of the cavern abruptly flew
open beside them, as though hinged like a door. Inside it was the mouth
of a soft-lit, man-high tunnel, and in its opening stood two men. They
wore over their clothing shroud-like, loose-hanging robes of gray,
asbestos-like material. They wore hoods of the same gray stuff over
their heads, pierced with slits at the eyes and mouth. And each wore on
his breast the blazing star-badge.

Through the eye-slits the eyes of the two surveyed Campbell and Ennis as
they halted, transfixed by the sudden apparition. Then one of the hooded
men spoke measuredly in a hissing, Mongolian voice.

"Are you who come here of the Brotherhood of the Door?" he asked,
apparently repeating a customary challenge.

Campbell answered, his flat voice tremorless. "We are of the
Brotherhood."

"Why do you not wear the badge of the Brotherhood, then?"

For answer, the inspector reached in his pocket for the strange emblem
and fastened it to his lapel. Ennis did the same.

"Enter, brothers," said the hissing, hooded shape, standing aside to let
them pass.

As they stepped into the tunnel, the hooded guard added in slightly more
natural tones, "Brothers, you two are late. You must hurry to get your
protective robes, for the ceremony soon begins."

Campbell inclined his head without speaking, and he and Ennis started
along the tunnel. Its light, as sourceless as that of the great
water-cavern, revealed that it was chiseled from solid rock and that it
wound downward.

When they were out of sight of the two hooded guards, Ennis clutched the
detective's arm convulsively.

"Campbell," he said, "the ceremony begins soon! We've got to find Ruth
f