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 the 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.