e tunnel seemed to pulse from that weird mechanism.

Up from that machine, if machine it was, soared the black basalt wall of
that end of the cavern. But there above the gray mechanism the rough
wall had been carved with a great, smooth facet, a giant, gleaming black
oval face as smooth as though planed and polished. Only, at the middle
of the glistening black oval face, were carven deeply four large and
wholly unfamiliar characters. As Ennis and Campbell stared frozenly
across the awe-inspiring place, sound swelled from the hundreds of
throats. A slow, rising chant, it climbed and climbed until the basalt
roof above seemed to quiver to it, crashing out with stupendous effect,
a weird litany in an unknown tongue. Then it began to fall.

Ennis clutched the inspector's gray-robed arm. "Where's Ruth?" he
whispered frantically. "I don't see any prisoners."

"They must be somewhere here," Campbell said swiftly. "Listen----"

As the chant died to silence, on the dais at the farther end of the
cavern the hooded man who wore the triple-jeweled star stepped forward
and spoke. His deep, heavy voice rolled out and echoed across the
cavern, flung back and forth from wall to rocky wall.

"Brothers of the Door," he said, "we meet again here in the Cavern of
the Door this year, as for ten thousand years past our forefathers have
met here to worship They Beyond the Door, and bring them the sacrifices
They love.

"A hundred centuries have gone by since first They Beyond the Door sent
their wisdom through the barrier between their universe and ours, a
barrier which even They could not open from their side, but which their
wisdom taught our fathers how to open.

"Each year since then have we opened the Door which They taught us how
to build. Each year we have brought them sacrifices. And in return They
have given us of their wisdom and power. They have taught us things that
lie hidden from other men, and They have given us powers that other men
have not.

"Now again comes the time appointed for the opening of the Door. In
their universe on the other side of it, They are waiting now to take the
sacrifices which we have procured for them. The hour strikes, so let the
sacrifices be brought."

As though at a signal, from a small opening at one side of the cavern a
triple file of marchers entered. A file of hooded gray members of the
Brotherhood flanked on either side a line of men and women who did not
wear the hoods or robes. They