still a mystery. So far the men had done practically nothing except
trail along after Layroh while he worked with his apparatus.

It was a state of affairs that caused the men little worry. As long as
they had enough to eat they were quite content. They were
down-and-outers, all of them, human derelicts recruited from the park
benches and cheap flop houses of Los Angeles. They had only one thing in
common: all of them were large and powerful men.

Don Foster was the youngest of the fifteen, and the only college man in
the group. A succession of bad breaks had finally landed him broke and
hungry on a park bench, where Layroh found him. Layroh's offer of ten
dollars a day and all expenses had seemed a godsend. Foster had promptly
jumped at the offer. Layroh's peculiar conditions and rules had seemed
trivial details at the time.

* * * * *

Foster scowled as he lit a cigarette and stared through the gloom at the
violet-lighted tent from which the disturbing sound still came. Seven
days of experience with Layroh's peculiarities had begun to make them a
little irritating. His sternly enforced code of rules was simple enough.
Never approach Layroh unless called. Never touch Layroh's instruments.
Never approach Layroh's tent. Never ask questions.

Layroh neither ate with the men nor mingled with them in any way that
could possibly be avoided. As soon as they made camp each night he set
up his small black tent and remained inside it until camp was broken the
next morning. No one knew whether the man ever slept. All night long the
violet light glowed inside the black tent. The men had wondered about
the unusual color of that light, then had finally decided it was
probably something required by the same eye weakness that made Layroh
wear heavily smoked goggles, both day and night.

Strange sounds in the night as Layroh worked with his apparatus in the
black tent were nothing unusual, but to-night was the first time that
Foster had ever heard this peculiar whining buzz. As he listened it rose
in a sudden thin crescendo that rippled along his spine like a file
rasping over naked nerve-ends. For one shuddering second there seemed to
be an intangible _living_ quality in that metallic drone, as though some
nameless creature sang in horrible exultance. Then abruptly the sound
ceased.

* * * * *

Foster drew a deep breath of relief and ground his cigarette into the