to wait and catch his pursuer as he
passed. So Olear sidled into the all but impenetrable underbrush and
slowly, with infinite caution, wormed his way along.

* * * * *

Presently he came to the little rise of ground where Morones had
disappeared, but a painstaking search did not reveal the factor. There
were, however, a number of other trails that joined the very faint
trail he had been following, and now there was a well-defined track
which continued to lead upward. With a grimace of disgust Olear again
plunged into the odorous underbrush and traveled parallel to the
trail. It was well he did so, for several Mercurians passed swiftly,
intent, so it seemed, in answering a shrill call that at times came
faintly to the ear. They carried slender spears.

Several more Mercurians passed. The growth was thinning out, and Olear
did not dare to proceed further. However, from his hiding place he
could discern a number of irregular cave openings, apparently leading
downward. They were apparently the entrances to one of the native
cavern colonies, or possibly of a meeting place. No Earthman had ever
entered one, but it was thought they had underground openings into the
river.

As the cave openings were obviously natural, Olear conjectured that
there might be others that were not used. After an anxious search he
found one, narrow and irregular, well hidden under the broad, glossy
leaves of some uncatalogued vegetation. As it showed no evidence of
use, Olear unhesitatingly slid down into it. It was very narrow and
irregular, so that often he was barely able to squeeze through. The
roots of trees choked the passage for a dozen feet or so, requiring
the vigorous use of a knife. Bathed in sweat, his uniform a filthy
mass of rags, Olear at last saw light.

The passage ended abruptly near the roof of a large natural cavern.
Lights glistened on stalactites which cut off Olear's larger view, and
voices came from below. By craning his neck the officer could look
between the pendent icicles of rock and see a fire burning on a huge
oblong block of stone. Figures were sitting on the floor around this
block--hundreds of Mercurians. The leaping flames made their white and
green faces and bodies look frog-like and less human than usual.

* * * * *

But the figure that dominated the whole assemblage, both by its own
hugeness and the magnetic power that flowed from it, was not