"Burl Denning! Can you hear me, Burl Denning?" A thin, tinny voice somewhere was calling him. But the darkness was all around, and Burl felt a great sleepiness and a desire only to sink deeper into the cottony nothing in which he seemed to be cradled. "Burl Denning! If you can hear me, speak up!" Again the faint, scratchy voice nagged at Burl's mind. He really ought to answer. He tried to open his mouth. Something hard and cold was pressing against his back. He tossed and squirmed. Once more the voice called, and this time he decided that he must be asleep. He struggled to open his eyes, then finally blinked them wide in an effort to adjust himself to his surroundings. He was apparently out in the open, and it was night. The sky was dark, not black, but almost so--a deep, blue-black. There was a pale blue saucer hanging in the sky. It blotted out most of the view. Gradually, he became aware of a shiny barrier between him and that sky--he was not out of doors. Something like a glass dome seemed to be overhead. Burl raised his head. There was no one in sight. He felt dizzy and confused. He lifted a hand to his brow, and felt the cold glass of his space helmet. He was still wearing his space suit then. The voice--it must be in his helmet phone. "Hello," he ventured weakly. "Who's calling?" Quickly the faint voice replied, growing stronger. "Burl, are you all right? Where are you?" Burl looked around. He was sitting on the floor of an isolated enclosure 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."