ded as close to the atomic power installation as
they dared. Now they would have to get closer. Somehow, one of them
had to get very near the reactor room, in order to activate the
Displacer.

Difficult. But Pid felt certain of success. After all, the Grom were
strong on ingenuity.

Strong on ingenuity, he thought bitterly, but terribly short of
radioactives. That was another reason why this expedition was so
important. There was little radioactive fuel left, on any of the Grom
worlds. Ages ago, the Grom had spent their store of radioactives in
spreading throughout their neighboring worlds, occupying the ones that
they could live on.

Now, colonization barely kept up with the mounting birthrate. New
worlds were constantly needed.

This particular world, discovered in a scouting expedition, was
needed. It suited the Grom perfectly. But it was too far away. They
didn't have enough fuel to mount a conquering space fleet.

Luckily, there was another way. A better way.

Over the centuries, the Grom scientists had developed the Displacer. A
triumph of Identity Engineering, the Displacer allowed mass to be
moved instantaneously between any two linked points.

One end was set up at Grom's sole atomic energy plant. The other end
had to be placed in proximity to another atomic power source, and
activated. Diverted power then flowed through both ends, was modified,
and modified again.

Then, through the miracle of Identity Engineering, the Grom could
_step_ through from planet to planet; or pour through in a great,
overwhelming wave.

It was quite simple.

But twenty expeditions had failed to set up the Earth-end Displacer.

What had happened to them was not known.

For no Grom ship had ever returned to tell.

* * * * *

Before dawn they crept through the woods, taking on the coloration of
the plants around them. Their Displacers pulsed feebly, sensing the
nearness of atomic energy.

A tiny, four-legged creature darted in front of them. Instantly, Ger
grew four legs and a long, streamlined body and gave chase.

"Ger! Come back here!" Pid howled at the Detector, throwing caution to
the winds.

Ger overtook the animal and knocked it down. He tried to bite it, but
he had neglected to grow teeth. The animal jumped free, and vanished
into the underbrush. Ger thrust out a set of teeth and bunched his
muscles for another leap.

"_Ger!_"

Reluctantly, the Detector turned away. He l