ptions on these walls, inspector, could you but
recognize them, carven in languages that perished from the face of earth
before Egypt was born. Yes, back through time, back through mediaeval and
Roman and Egyptian and pre-Egyptian ages, the Brotherhood of the Door
has existed and has each year gathered in this place to open the Door
and worship with sacrifices They Beyond it."

The fanatic note of unearthly devotion was in his voice now, and Ennis
shuddered with a cold not of the tunnel.

As they proceeded, they heard a muffled, hoarse booming somewhere over
their heads, a dull, rhythmic thunder that echoed along the long
passageway. The walls of the tunnel now were damp and glistening in the
sourceless soft light, tiny trickles running down them.

"You hear the ocean over us," came Chandra Dass' voice. "The Cavern of
the Door lies several hundred yards out from shore, beneath the rock
floor of the sea."

They passed the dark mouths of unlit tunnels branching ahead from this
illuminated one. Then over the booming of the raging sea above them,
there came to Ennis' ears the distant, swelling chant they had heard in
the water-cavern above. But now it was louder, nearer. At the sound of
it, Chandra Dass quickened their pace.

Suddenly Inspector Campbell stumbled on the slippery rock floor and went
down in a heap. Instantly Chandra Dass and his two followers recoiled
from them, the two pistols trained on the detective as he scrambled up.

"Do not do that again, inspector," warned the Hindoo in a deadly voice.
"All tricks are useless now."

"I couldn't help slipping on this wet floor," complained Inspector
Campbell.

"The next time you make a wrong step of any kind, a bullet will smash
your spine," Chandra Dass told him. "Quick--march!"

* * * * *

The tunnel turned sharply, turned again. As they rounded the turns,
Ennis saw with a sudden electric thrill of hope that Campbell held
clutched in his hand, concealed by his sleeve, the heel-hilted knife
from his shoe. He had drawn it when he stumbled.

Campbell edged a little closer to the young American as they were
hastening onward, and whispered to him, a word at a time.

"Be--ready--to jump--them----"

"But they'll shoot, your first move----" whispered Ennis agonizedly.

Campbell did not answer. But Ennis sensed the detective's body
tautening.

They came to another turn, the strong, swelling chant coming loud from
ahead. They s