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 loped silently back to Pid.

"I was hungry," he said.

"You were not," Pid said sternly.

"Was," Ger mumbled, writhing with embarrassment.

Pid remembered what the Chief had told him. Ger certainly did have Hunter tendencies. He would have to watch him more closely.

"We'll have no more of that," Pid said. "Remember—the lure of Exotic Shapes is not sanctioned. Be content with the shape you were born to."

Ger nodded, and melted back into the underbrush. They moved on.

At the extreme edge of the woods they could observe the atomic energy installation. Pid disguised himself as a clump of shrubbery, and Ger formed himself into an old log. Ilg, after a moment's thought, became a young oak.

The installation was in the form of a long, low building, surrounded by a metal fence. There was a gate, and guards in front of it.

The first job, Pid thought, was to get past that gate. He began to consider ways and means.

From the fragmentary reports of the survey parties, Pid knew that, in some ways, this race of Men were like the Grom. They had pets, as the Grom did, and homes and children, and a culture. The inhabitants were skilled mechanically, as were the Grom.

But there were terrific differences, also. The Men were of fixed and immutable form, like stones or trees. And to compensate, their planet boasted a fantastic array of species, types and kinds. This was completely unlike Grom, which had only eight distinct forms of animal life.

And evidently, the Men were skilled at detecting invaders, Pid thought. He wished he knew how the other expeditions had failed. It would make his job much easier.

  Man lurched past them on two incredibly stiff legs. Rigidity was evident in his every move. Without looking, he hurried past.

"I know," Ger said, after the creature had moved away. "I'll disguise myself as a Man, walk through the gate to the reactor room, and activate my Displacer."

"You can't speak their language," Pid pointed out.

"I won't speak at all. I'll ignore them. Look." Quickly Ger shaped himself into a Man.

"That's not bad," Pid said.

Ger tried a few practice steps, copying the bumpy walk of the Man.

"But I'm afraid it won't work," Pid said.

"It's perfectly logical," Ger pointed out.

"I know. Therefore the other expeditions must have tried it. And none of them came back."

There was no arguing that. Ger flowed back into the shape of a log. "What, then?" he asked.

"Let me think," Pid said.

Another creature lurched past, on four legs instead of two. Pid recognized it as a Dog, a pet of Man. He watched it carefully.

The Dog ambled to the gate, head down, in no particular hurry. It walked through, unchallenged, and lay down in the grass.

"H'm," Pid said.

They watched. One of the Men walked past, and touched the Dog on the head. The Dog stuck out its tongue and rolled over on its side.

"I can do that," Ger said excitedly. He started to flow into the shape of a Dog.

"No, wait," Pid said. "We'll spend the rest of the day thinking it over. This is too important to rush into."

Ger subsided sulkily.

"Come on, let's move back," Pid said. He and Ger started into the woods. Then he remembered Ilg.

"Ilg?" he called softly.

There was no answer.

"Ilg!"

"What? Oh, yes," an oak tree said, and melted into a