dead voice asked. "I want Judd. Where is Judd?"

"Judd is dead. The trap failed, and there was a fight on Iapetus. Judd
was killed by Carse, and most of the others. Only two of us are left,
but we have Carse and the negro, prisoners, alive. What are your
instructions?"

A half minute went by, and the three men hardly breathed.

"How do we know you are Sako?" said the voice at last. "Give the
recognition."

"The insignia of Dr. Ku Sui?"

"Yes. It is----"

Carse's ray-gun prodded the stomach of the sweating Sako.

"An asteroid," he said hastily, "in the center of a circle of the ten
planets."

The unseen speaker was quiet. Evidently he was conferring with someone
else, probably Ku Sui.

"All right," his toneless voice came back at last. "You will remain
motionless in your present position, keeping your radio receiver open
for further instructions. We are approaching and will be with you in
thirty minutes."

Carse motioned to Friday to switch off the mike. Sako sank limply into a
chair, soaked with perspiration.

"Now we must wait again," the Hawk murmured, crossing his arms and
scanning the visi-screen.

* * * * *

They had heard from Ku Sui, but that had not answered the old tormenting
question of how he would come. It was more puzzling than ever. The
visi-screen showed nothing, and it should have shown the Eurasian's
decelerating ship even at twice thirty minutes' time away. They looked
upon the same vista of Jupiter and his satellites, framed in eternal
blackness; there was no characteristic steely dot of an approaching ship
to give Carse the enemy's position and enable him to shape his plan of
reception definitely.

Twenty minutes went by. The strain the Hawk was under showed only in his
pulling at the bangs of flaxen hair that covered his forehead as far as
the eyebrows. He had, from Judd's words, expected a mystery in Ku Sui's
approach. There was nothing to do but wait; he had made what few plans
and preparations he could in advance.

Friday broke the tense silence in the control cabin. "He's _got_ to be
_somewhere_!" he exploded. "It isn't natural for the screen not to show
nothin'! Isn't there somethin' we can do?"

The Hawk was surprisingly patient. "I'm afraid not," he said. "It's
invisibility he's using, or else the fourth dimension, as Judd said. But
we've got one good chance. He'll send more instructions by radio, and
surely, after that, his ship