full.

"What about you?" he said to Ward. "You can't go back."

"Nah. I'll have to go with you. Warm her up, Duke, while I open the
dome."

He darted out. Gray set the atmosphere motors idling. The dome slid
open, showing the flicker of the auroras, where areas of intense heat
and cold set up atmospheric tension by rapid fluctuation of adjoining
air masses.

Mercury, cutting the vast magnetic field of the Sun in an eccentric
orbit, tortured by the daily change from blistering heat to freezing
cold in the thin atmosphere, was a powerful generator of electricity.

Ward didn't come back.

Swearing under his breath, tense for the sound of pursuit in spite of
the girl, Gray went to look. Out beyond the hangar, he saw a figure
running.

Running hard up into the narrowing cleft of the valley, where natural
galleries in the rock of Mercury led to the places where the copper
cables were anchored, and farther, into the unexplored mystery of the
caves.

Gray scowled, his arrogant Roman profile hard against the flickering
aurora. Then he slammed the lock shut.

The ship roared out into the tearing winds of the plain. Gray cut in his
rockets and blasted up, into the airless dark among the high peaks.

Jill Moulton hadn't moved or spoken.

Gray snapped on the space radio, leaving his own screen dark. Presently
he picked up signals in a code he didn't know.

"Listen," he said. "I knew there was some reason for Ward's running out
on me."

His Indianesque face hardened. "So that's the game! They want to make
trouble for you by letting me escape and then make themselves heroes by
bringing me in, preferably dead.

"They've got ships waiting to get me as soon as I clear Mercury, and
they're getting stand-by instructions from somebody on the ground. The
somebody that Ward was making for."

Jill's breath made a small hiss. "Somebody's near the Project...."

Gray snapped on his transmitter.

"Duke Gray, calling all ships off Mercury. Will the flagship of your
reception committee please come in?"

His screen flickered to life. A man's face appeared--the middle-aged,
soft-fleshed, almost stickily innocent face of one of the Solar Systems
greatest crusaders against vice and crime.

Jill Moulton gasped. "Caron of Mars!"

"Ward gave the game away," said Gray gently. "Too bad."

The face of Caron of Mars never changed expression. But behind those
flesh-hooded eyes was a cunning brain, working at top speed.

"I have a p