e wave of boiling mud arose in the air. Garin choked
in a wind, thick with chemicals, which blew from it. He smelled and
tasted the sulphur-tainted air all across the plain.

And he was glad enough to plunge into a small fern grove which
half-concealed a spring. There he bathed his head and arms while the Ana
pulled open Sera's food bag.

Together they ate the cakes of grain and the dried fruit. When they were
done the Ana tugged at Garin's hand and pointed on.

Cautiously Garin wormed his way through the thick underbrush until, at
last, he looked out into a clearing and at its edge the entrance of the
Black Ones' Caves. Two tall pillars, carved into the likeness of foul
monsters, guarded a rough-edged hole. A fine greenish mist whirled and
danced in its mouth.

The flyer studied the entrance. There was no life to be seen. He gripped
the destroying rod and inched forward. Before the green mist he braced
himself and then stepped within.

_CHAPTER SIX_

_Kepta's Second Prisoner_

The green mist enveloped Garin. He drew into his lungs hot moist air
faintly tinged with a scent of sickly sweetness, as from some hidden
corruption. Green motes in the air gave forth little light and seemed to
cling to the intruder.

With the Ana pattering before him, the American started down a steep
ramp, the soft soles of his buskins making no sound. At regular
intervals along the wall, niches held small statues. And about each
perverted figure was a crown of green motes.

The Ana stopped, its large ears outspread as if to catch the faintest
murmur of sound. From somewhere under the earth came the howls of a
maddened dog. The Ana shivered, creeping closer to Garin.

Down led the ramp, growing narrower and steeper. And louder sounded the
insane, coughing howls of the dog. Then the passage was abruptly barred
by a grill of black stone. Garin peered through its bars at a flight of
stairs leading down into a pit. From the pit arose snarling laughter.

Padding back and forth were things which might have been conceived by
demons. They were sleek, rat-like creatures, hairless, and large as
ponies. Red saliva dripped from the corners of their sharp jaws. But in
the eyes, which they raised now and then toward the grill, there was
intelligence. These were the morgels, watchdogs and slaves of the Black
Ones.

From a second pair of stairs directly across the pit arose a moaning
call. A door opened and two men came down the steps. T