and fell to the
ground, dragging the unseen Kashtanov with him. And as he pitched into
the damp grass, the shock dislodged his grip.

He was up in a flash, but the damage was done. The monkey-wrench
curved through the darkness in a vicious swipe that landed it flush
against his jaw; swung back, pounded again like a trip-hammer--again
and again and again....

Chris reeled back, teetered on the edge of nothingness, then went
tumbling crazily down into the sand-trap behind. One leg was doubled
underneath him as he crashed.

A voice floated down out of the darkness. "That is the end of you!" it
said. But Chris Travers did not hear it....

* * * * *

Pain. Agonizing pain. The whole lower side of his face was a burning,
throbbing, aching lump of flesh, and his left leg seemed on fire. What
had happened? Where was he?

Then came remembrance, and it was far worse than the fangs of pain
that were gnawing him. Chris cried out--a cracked, twisted cry.
Kashtanov, the dam--the box of the ray! How much time had passed?

He hunched his body over and stared up. Limned against the starlight
were the wings of a plane, still standing where it had landed beside
the sand-trap. He clutched his thoughts. The plane meant--it meant
Kashtanov had gone on his errand, had not yet returned? Only minutes
had gone by since the blows from the monkey-wrench. But was the box
placed yet? Was Kashtanov already hurrying back?

He listened. From far away came a drone that was separate from the
throbbing of his head. The drone of waters, controlled waters. The
normal sound of the spillway of Gatun Dam. The box had not yet
unleashed its disintegrating bolt of blue.

"I've got to stop it!" he whispered.

He tried to rise. Only one leg held. The other twisted awrily with a
rasp of broken bones. A spearing pain tore through him. Useless! His
fall had broken it. He could not rise, could not walk, much less run.
He was no more than a cripple.

"Oh, God!" he groaned, "How can I, how can I?"

Then his eyes fell on the plane resting above him.

"I've got one leg," he muttered, "and two hands and two eyes....
They're left me. Yes!"

He rolled over. He shoved with his right leg and clawed at the bank of
the sand-trap. Inch by inch he wormed up, slipping, scraping. The sand
grated into his battered face and seeped through onto his tongue; he
coughed and spluttered, groaning from the effort and his feebleness.
Spots of b