weapon. He
was in the doorway, his ray sweeping the platform clear.

Darl was out now, stepping into the flier that still hung by its
hooked moorings. Jim caught a flash of blue and looked up. The Martian
was hanging to a girder just above, his green tube pointing straight
at Darl. A white ray spurted from Jim's gun. The Martian's weapon and
the hand that held it vanished in the sizzling blast. The plane was
loose! Jim leaped inside the air-lock, slammed the steel door shut,
clamped it, and sprang for the quartz peer-hole.

* * * * *

Darl's gyrocopter was diving on a long slant for the Dome wall. Faster
and faster it went, till all Jim could see was a white streak in the
smoky dimness. And now he could see the vast interior, the teeming
plain, the dwarf-festooned girders and roof-beams. He stood rigid,
waiting breathlessly. Then the plane struck--fair in the center of a
great panel of quartz. The wall exploded in a burst of flying,
shattered splinters. A deafening crash rocked the Dome.

Jim clung to his port-hole, tears rolling down his cheeks, unashamed.
The plane, and Darl, vanished. Jim saw the black smoke masses whirl
through the jagged hole in the Dome's wall as the air burst out in a
cyclonic gust. He saw the vast space filled with falling Mercurians,
saw a blue form plunge down and crash far below. He knew that in all
that huge hemisphere, and in the burrows beneath it, there was no life
save himself, and Angus, and the faithful Ran-los. For only in this
compartment that clung to the roof of the Dome was there left air to
breathe. And, from the void beyond, the silver space ship sped on
toward Mercury, sped on to a safe landing that, but for Darl Thomas's
sacrifice, would have been her doom....

Guided by Jim and Angus, a party of men from the battle-flier,
equipped with oxygen respirators, went to the aid of Darl. They dug
him out from under his crumpled plane and the piled splinters of
quartz. His metal was dented and twisted, but unpierced. They carried
him tenderly to the space ship, and carefully set him down. The ship's
physician listened long with his stethoscope, then looked up and
smiled.

"He's alive," the doctor said, "just barely alive. The thick padding
of bandages must have saved him from the full shock of the crash.
They're hard to kill, these ITA men. I'll be able to bring him around,
God willing."

* * * * *

En