ontrol-tubes of the portes had flashed into a close-circuit and
burned out. The admission portes would not open!

"And the pressure controls smashed! Broken from outside--!"

There was no way now of getting out through these pressure-locks. The
doors, the entire pressure-lock system, was dead. Had it been tampered
with from outside?

As though to answer Grantline's amazed question there came a chorus of
shouts from the men at the corridor windows.

"Commander! By God--look!"

A figure was outside, close to the building! Clothed in suit and
helmet, it stood, bloated and gigantic. It had evidently been lurking
at the porte-entrance, had ripped out the wires there.

It moved past the windows, saw the staring faces of the men, and made
off with giant bounds. Grantline reached the window in time to see it
vanish around the building corner.

It was a giant figure, larger than a normal Earthman. A Martian?

* * * * *

Up on the summit of the crater the two small figures were still
fighting. All this turmoil had taken no more than a minute or two.

A lurking Martian outside? The brigand, Miko? More than ever,
Grantline was determined to get out. He shouted to his men to don some
of the other suits, and called for some of the hand bullet projectors.

But he could not get out through these main admission portes. He could
have forced the panels open perhaps; but with the pressure-changing
mechanisms broken, it would merely let the air out of the corridor. A
rush of air, probably uncontrollable. How serious the damage was no
one could tell as yet. It would perhaps take hours to repair it.

Grantline was shouting. "Get those weapons! That's a Martian outside!
The brigand leader, probably! Get into your suits, anyone who wants to
go with me! We'll go by the manual emergency exit!"

But the prowling Martian had found it! Within a minute Grantline was
there. It was a smaller, two-lock gateway of manual control, so that
the person going out could operate it himself. It was in a corridor at
the other end of the main building. But Grantline was too late! The
lever would not open the panels!

Had someone gone out this way and broken the mechanisms after him? A
traitor in the camp? Or had someone come in from outside? Or had the
skulking Martian outside broken this lock as he had broken the other?

The questions surged on Grantline. His men crowded around him. The
news spread. The camp was a p