ence for a few moments, and then Sam asked, "Want to
go on?"

"I want to finish my studying."

That was something new. "Okay," said Sam, and turned back.

* * * * *

They were approaching the ship when the sound of a pebble falling came
to Sam's ears. Automatically, his hand reached for his gun, and he swung
around to face what might be danger. As he did so, something snarled and
fled. He could see no sign of motion, but he could hear the scattering
of other pebbles along a gully as the creature retreated.

"Looks like we're not alone here, after all," he said. "Wonder what that
was."

"It couldn't have been very big," said Mark. "Big animals don't run
away."

"Not usually, unless they're smart, or they've met people before. I'll
have to set traps."

"Do you think maybe if you caught him you could sell him to a circus,
Pop?"

"I'll have to see what he's like, first," said Sam. He looked around.
"If there's one animal, there are likely to be others. It's strange that
I didn't detect any sign of them."

He put his arm absently over Mark's shoulder. He didn't notice the
expression on the kid's face at this unexpected gesture.

[Illustration]

When they were inside the ship again, Mark said, "Guess I'd better get
back to my arithmetic."

"In a minute," said Sam. "I want to talk to you first." He dropped
wearily into a seat, although he had done nothing that should have tired
him out. His son looked at him expectantly. "Mark, do you like traveling
around with me?"

"Sure, Pop, I like to be with you."

"Not seeing anybody else? No other kids, no people of any kind? Just
being with me, learning your lessons from tapes, and having your test
papers corrected automatically? You don't get tired of it?"

Mark hesitated despite himself. Then he said loyally, "I'd rather be
with you than anybody else. When Mom--when Mom died--I didn't want to
see anybody."

"I know how you felt. But that was four years ago. You can't grow up
alone. Now what you need to do is meet people, learn how they talk and
think and feel. You can't learn those things from tapes, and you can't
learn them from me."

Mark said stubbornly, "I like to be with you."

"I'm not much of a person to be with. Don't think I don't know it. I'm
mean and surly, and my temper's getting worse by the day. I can't
associate with people any more. But _you_ can. I was thinking maybe I'd
leave you--"

"No!" cried Mark.

"N