losure
with a transparent dome. There were no walls, just the rounded dome like
a fishbowl turned upside down on him. The flooring beneath his feet was
plastic.

"I'm all right, I think," said Burl. "Is that you, Russ? Sounds a little
like you, but you must be far away."

"Yes, it's me, Russell Clyde," confirmed the voice. "You're coming in
weak, too. Where are you?"

Burl described his surroundings. There was a silence for a moment, then
Russ's voice again. "I kind of suspected it, but what you say confirms
it. We must be on the only planet we haven't visited ... or rather, not
on it, but near it. I mean Neptune. I knew from the gravity I wasn't on
Pluto any more. Judging from our weight, and your description of the
bluish planet in the sky, we must be on Triton, Neptune's bigger moon."

Burl found that his dizziness was disappearing. "I feel light," he
commented, as he got to his feet. "Should Neptune look sort of like
Uranus, only more bluish in color?" he asked.

"That's it," said Russ. "Neptune is pretty much of a twin for Uranus,
only it's denser, a little bit smaller, and perhaps more substantial
than the other giant worlds in our system. It should have a second moon,
smaller and way out."

Burl walked around the little enclosed space. "I guess I'm a prisoner
here," he said. "This dome is on the surface. Most of the area is just a
sort of rocky plain with patches of liquid gases, but there are a couple
of big buildings nearby. Funny sort of structures--they have fancy tops
with symbols on them that look like the phases of the moon."

"I think I'm inside one of those buildings," Russ guessed. "I'm in a big
hall with a lot of exhibits in glass cases. And they've got the
strangest creatures I've ever seen in them. There are lunar markings
here, too--they remind me of the ones we saw on Pluto. You know what I
suspect?"

Burl paced around, regaining his senses as he walked. It was obvious
that, after he'd been knocked out by the Plutonians, he had been taken
by them to this moon of Neptune. For what purpose?

Russ continued to murmur his thoughts, his voice ringing tinnily in
Burl's earphones. "I think that Triton was originally Pluto's moon. When
Pluto wandered into the solar system, it crossed Neptune's orbit and was
held. Its moon came closer to Neptune and was captured completely. But
Pluto, having a greater mass, didn't stick. It established an eccentric
orbit of its own which took it far out from Nept