jack when the colonel's orderly found
him. He hastily buttoned his tunic and in a few minutes, alert and
very military, was standing at attention in the little office on the
ground floor of the Denver I. F. P. barracks. His swanky blue uniform
fitted without a wrinkle. His little round skullcap was perched at the
regulation angle.

"Olear," said the colonel, "they're having a little trouble at the
Blue River Station, Mercury."

"Trouble? Uh-huh," Olear said placidly.

The colonel looked him over. He saw a man past his first youth.
Thirty-five, possibly forty. Olear was well-knit, sandy-haired, not
over five feet six inches in height. His hair was close-cropped, his
features phlegmatic, his eyes a light blue with thick, short,
light-colored lashes, his teeth excellent. A scar, dead white on a
brown cheekbone, was a reminder of an "encounter" with one of the
numerous sauriens of Venus.

"I'm sending you," explained the colonel, "because you're more
experienced, and not like some of these kids, always spoiling for a
fight. There's something queer about this affair. Morones, factor of
the Blue River post, reports that his assistant has disappeared.
Vanished. Simply gone. But only three months ago the former
factor--Morones was his assistant--disappeared. No hide nor hair of
him. Morones reported to the company, the Mercurian Trading
Concession, and they called me. Something, they think, is rotten."

"Yes, sir."

"I guess I needn't tell you," the colonel went on, "that you have to
use tact. People don't seem to appreciate the Force. What with the
lousy politicians begrudging every cent we get, and a bunch of
suspicious foreign powers afraid we'll get too good--"

"Yeah, I know. Tact, that's my motto. No rough stuff." He saluted,
turned on his heel.

"Just a minute!" The colonel had arisen. He was a fine, ascetic type
of man. He held out his hand.

"Good-by, Olear. Watch yourself!"

When Olear had taken his matter-of-fact departure the colonel ran his
fingers through his whitening hair. In the past several months he had
sent five of his best men on dangerous missions--missions requiring
tact, courage, and, so it seemed, very much luck. And only two of the
five had come back. In those days the Interplanetary Flying Police did
not enjoy the tremendous prestige it does now. The mere presence of a
member of the Force is enough, in these humdrum days of interplanetary
law and order, to quell the most serious disturba