ey flew on, over the desert, until the Gray Mountains loomed on the
horizon. On, over the tumbled rocks, interspersed with the strange red
thorny vegetation common in the Martian desert.

Far below them, in a ravine, a cylindrical building was now visible,
and toward this the car began to drop. It landed on a level space
before the structure. A sliding gate opened, and the car wheeled into
a sort of courtyard, protected from the cold of night by an arching
roof of glass.

Sime was hustled out and led into an office located on the lower floor
of the fortification, or whatever the structure was.

As he saw the man who sat at the desk he gave a startled explanation.

"Colonel Barkins!"

* * * * *

The elderly, white-haired man smiled. He brushed back his hair with a
characteristic gesture, and his twinkling blue eyes bored into those
of the I. F. P. special officer. The colonel wore the regular uniform
of the service; his little skullcap, with the conventionalized sun
symbol denoting his rank, was on the table before him. He put out his
lean, strong hand.

"Surprised to see me, eh, Hemingway?" he inquired pleasantly.

Sime managed an awkward salute. "I don't quite understand, sir. You
gave me my instructions at the Philadelphia space port just before I
made the _Pleadisia_. She's the fastest passenger liner in the solar
system: I've barely landed here, and it seems you got here before me.
It don't seem right!"

Sime watched the colonel narrowly, a vague suspicion in his mind, and
he thought he saw a slight flicker in the man's eye when Sime spoke.

But the colonel answered smoothly, with a hint of reproof.

"Never mind questioning me now, Hemingway. The mission is important. I
want to know if you remember every detail of what I told you." He
nodded to the men, and they filed out of the room. "Repeat your
orders."

"Nothing doing, Colonel!" Sime replied promptly and respectfully. "In
fact, Colonel, you can go to hell! This is the first time that a man
of the I. F. P. has turned traitor, and if your men hadn't so
thoughtfully taken my neuro I'd be pleased to finish you right now!"

"But you observe I have a neuro in my hand," remarked the colonel
pleasantly, "and so you will remain standing where you are."

* * * * *

So saying, he slipped off the white wig he was wearing, wiped his face
so that the brown powder came off, and sat, obviously pleas