at his face
was covered with plasters. Then, startled, he saw that Leon was
shivering as with the ague. His outline on the screen grew dim and
indistinct as the rate of vibration increased. Then the body bloated and
became misty. He could see through it. The vibrating death! His father
had gone the same way!

Karl groaned at the thought. The whine of the distant machine rose in
pitch until it passed the limit of audibility. Tiny pin-points of
incandescence glowed here and there from the Zar's victims as periods of
vibration were reached that coincided with the natural periods of
certain of the molecules of their structure. They were no longer
recognizable as human beings. Shimmering auras surrounded them. Suddenly
they were torches of cold fire, weaving, oscillating with inconceivable
rapidity. Then they were gone; vanished utterly.

The Zar laughed--that horrible cackle again.

"Great God!" exclaimed Karl, "let's go! The fiend must not live a moment
longer than necessary. Are you ready?"

Rudolph's brother smiled. "We're ready Karl," he said.

* * * * *

The great vessel hummed with activity. The five torpedo-shaped aeros of
the battle fleet were ready to take off from the cavities in the hull.
In the flagship Karl was stationed at the control of the heat-ray. His
instructions in its operation had been simple. A telescopic sight with
crosshairs for the centering of the object to be attacked; a small
lever. That was all. He burned with impatience.

Then they were dropping; falling clear of the mother ship. The pilot
pressed a button and the electronic motors started. A burst of roaring
energy streamed from the tapered stern of their vessel and the earth
lurched violently to meet them. Down, down they dived until the rocking
surface of Dorn was just beneath them. Then they flattened out and
circled the vast upper surface. From the corner of his eye Karl saw that
the other four vessels of his fleet were just behind. There was a flurry
among the wasplike clouds of pleasure craft over the city. They scurried
for cover. Something was amiss!

"Hurry!" shouted Karl. "The warning is out! There is no time to lose!"

He pressed his face to the eye-piece of his sight, his finger on the
release lever of the ray. The crystal pyramid crossed his view and was
gone. Again it crossed, more slowly this time. And now his sight was
dead on it, the gleaming wall rushing toward him. Pressure on the ti