my secret base, _this_ my hidden laboratory. I take it always with
me, and I travel where I will."

The Hawk nodded coldly his acceptance of the astounding fact; he was too
busy to make comment. He was observing the buildings, the nature of
them, the exits from the dome, how they could best be reached.

* * * * *

They stood on the roof of the largest and central building, a low metal
structure with four wings, crossing at right angles to make the figure
of a great plus mark. The hub was probably Dr. Ku's chief laboratory,
Carse conjectured. On each side stood other buildings, low, long, like
barracks, with figures of coolies moving in and out. Workshops, living
quarters, power-rooms, he supposed: power-rooms certainly, for a soft
hum filled the air.

There were two great port-locks at ground level in the dome, one on each
side, each sizable enough to admit the largest space-ship and each
flanked by a smaller, man-sized lock. To reach them....

"And over there," Dr. Ku's voice broke in, "you see your borrowed ship,
the _Scorpion_. But please don't let it tempt you to cut short your
visit with me, my friend. It would avail you nothing even if you reached
her, for it requires a secret combination to open the port-locks, and my
servants' brains have been so altered that they are physically incapable
of divulging it to you. And of course I have offensive rays and other
devices hidden about--just in case. All rather hopeless, isn't it? But
surely interesting.

"Let us go: I have more. Below, in my main laboratory in the center of
this building, there's something far more interesting, and it concerns
you, Carse, and me, and also Master Scientist Eliot Leithgow." He let
the words sink in. "Will you follow me?"

And so they went below again, down the spider ladder into the corridor.
There was nothing else to do: the guards, ever watchful, pressed close
behind. But a tattoo of alarm was beating in Hawk Carse's brain. Eliot
Leithgow again--the hint of something ominous to be aimed at him, Carse,
for the extraction of information he alone possessed: the whereabouts of
his elderly friend the Master Scientist.

CHAPTER V

_The Color-Storm_

The corridor was stopped by a heavy metal door. As the small party
approached, it swung inward in two halves, and a figure clad in a white
surgeon's smock emerged. He was a white man, tall, with highly
intelligent face but eyes strangel