t point of white light in the
center of the pilot's closely ruled micrometer grating, exactly upon the
cross-hairs of his directors, showed that the immense vessel was
precisely upon the calculated course, as laid down by the automatic
integrating course plotters. Everything was quiet and in order.

"All's well, sir," he reported briefly to Captain Bradley--but all was
not well.

Danger--more serious by far in that it was not external--was even then,
all unsuspected, gnawing at the great ship's vitals. In a locked and
shielded compartment, deep down in the interior of the liner, was the
great air purifier. Now a man leaned against the primary duct--the aorta
through which flowed the stream of pure air supplying the entire vessel.
This man, grotesque in full panoply of space armor, leaned against the
duct, and as he leaned a drill bit deeper and deeper into the steel wall
of the pipe. Soon it broke through, and the slight rush of air was stopped
by the insertion of a tightly fitting rubber tube. The tube terminated in
a heavy rubber balloon, which surrounded a frail glass bulb. The man stood
tense, one hand holding before his silica-and-steel-helmeted head a large
pocket chronometer, the other lightly grasping the balloon. A sneering
grin was upon his face as he waited the exact second of action--the
carefully predetermined instant when his right hand, closing, would
shatter the fragile flask and force its contents into the primary air
stream of the _Hyperion_!

* * * * *

Far above, in the main saloon, the regular evening dance was in full
swing. The ship's orchestra crashed into silence, there was a patter of
applause, and Clio Marsden, radiant belle of the voyage, led her partner
out onto the promenade and up to one of the observation plates.

"Oh, we can't see the Earth any more!" she exclaimed. "Which way do you
turn this, Mr. Costigan?"

"Like this," and Conway Costigan, burly young First Officer of the
liner, turned the dials. "There--this plate is looking back, or down, at
Tellus; this other one is looking ahead."

Earth was a brilliantly shining crescent far beneath the flying vessel.
Above her, ruddy Mars and silvery Jupiter blazed in splendor ineffable
against a background of utterly indescribable blackness--a background
thickly besprinkled with dimensionless points of dazzling brilliance
which were the stars.

"Oh, isn't it wonderful!" breathed the girl, awed. "Of cours