In the
robes and concealing hoods, they could not be told from any other two
members of the Brotherhood, except that the badge on Ennis' breast was
the double star instead of the single one.

Ennis then spun toward the main, lighted tunnel, Campbell close behind
him. They recoiled suddenly into the darkness of the branching way, as
they heard hurrying steps out in the lighted passage. Flattened in the
darkness against the wall, they saw several of the gray-hooded members
of the Brotherhood hasten past them from above, hurrying toward the
gathering-place.

"The guards and robe-issuers we saw above!" Campbell said quickly when
they were passed. "Come on, now."

He and Ennis slipped out into the lighted tunnel and hastened along it
after the others.

Boom of thundering ocean over their heads and rising and falling of the
tremendous chanting ahead filled their ears as they hurried around the
last turns of the tunnel. The passage widened, and ahead they saw a
massive rock portal through whose opening they glimpsed an immense,
lighted space.

Campbell and Ennis, two comparatively tiny gray-hooded figures, hastened
through the mighty portal. Then they stopped. Ennis felt frozen with the
dazing shock of it. He heard the detective whisper fiercely beside him.

"It's the Cavern, all right--the Cavern of the Door!"

* * * * *

They looked across a colossal rock chamber hollowed out beneath the
floor of ocean. It was elliptical in shape, three hundred feet by its
longer axis. Its black basalt sides, towering, rough-hewn walls, rose
sheer and supported the rock ceiling which was the ocean floor, a
hundred feet over their heads.

This mighty cathedral hewn from inside the rock of earth was lit by a
soft, white, sourceless light like that in the main tunnel. Upon the
floor of the cavern, in regular rows across it, stood hundreds on
hundreds of human figures, all gray-robed and gray-hooded, all with
their backs to Campbell and Ennis, looking across the cavern to its
farther end. At that farther end was a flat dais of black basalt upon
which stood five hooded men, four wearing the blazing double-star on
their breasts, the fifth, a triple-star. Two of them stood beside a
cubical, weird-looking gray metal mechanism from which upreared a
spherical web of countless fine wires, unthinkably intricate in their
network, many of them pulsing with glowing force. The sourceless light
of the cavern and th