The air lock hissed, then slid open. A Martian stood in the entryway, a case on his shoulder. Rip watched him with interest. He had seen Martians before, on the space platform, but he had never gotten used to them. They were human, still.... He tried to figure out, as he had before, what it was that made them strange. It wasn’t the blue-whiteness of their skins nor the very large, expressionless eyes. It was something about their bodies. He studied the Martian’s figure carefully. He was slightly taller and more slender than the average earthman, but his chest measurements would be about the same. Nor were his legs very much longer. Suddenly Rip thought he had it. The Martian’s legs and arms joined his torso at a slightly different angle, giving him an angular look. That was what made him look like a caricature of a human. Although he was human, of course. As human as any of them. Rip saw that other Martians were in the air lock, all carrying cases of various sizes and shapes. They came through into the control room and put them down, then turned without a word and hurried back into the lock. They were all breathing heavily, Rip noticed. Of course! The artificial atmosphere inside the space ship must seem very heavy and moist to them after the thin, dry air of Mars. The lock worked and the Martians were replaced by others. They, too, deposited their cases. But these cases were bigger and heavier. It took four Martians to carry one, which meant they weighed close to half a ton each. The Martians could carry more than double an earthman’s capacity. When the lock worked next time, a Planeteer captain came in. He breathed the heavy air appreciatively, fingering the oxygen mask he had to wear outside. He saluted Commander O’Brine and reported, "This is all, sir. We filled the order exactly as Terra sent it. Is there anything else you need?" O’Brine turned to his deputy. "Find out," he ordered. "This is our last chance. We have plenty of basic supplies, but we may be short of audio-mags and other things for the men." He turned his back on the Planeteer captain and walked away. The captain grinned at O’Brine’s retreating back, then walked over to Rip. They shook hands. "I’m Southwick, SOS Two. Canadian." Rip introduced himself and said he was an American. He added, "And aside from my men, you’re the first human being I’ve seen since we made space." Southwick chuckled. "Trouble with the spacemen? Well, you’re not the first." Talking about assignments wasn’t considered good practice, but Rip was burning with curiosity. "You don’t by chance know what my assignment is, do you?" The captain’s eyebrows went up. "Don’t you?" Rip shook his head. "O’Brine hasn’t told me." "I don’t know a thing," Southwick said. "We got instructions to pack up a pretty strange assortment of supplies for the _Scorpius_ and that’s all I know. The order was in special cipher, though, so we’re all wondering about it."