“Inside the Hornfield crater,” Mac answered.

“Are there any settlements close by?” the captain asked. “Anybody who can come to our rescue?”

“About twenty-five miles to the southwest, captain,” Mac answered. “Ben told me just where it was and advised me to land as close to it as possible. I thought this was as close as we dared approach, because the ground is treacherous between Hornfield and the settlement.”

“What sort of settlement is it, Mac?” Isaac asked.

“An oxygen-mining outfit in the Taurus Mountains. They’re mining for ore rich in oxygen to provide pressurized air for the underground terminal of Luna City, five hundred miles farther to the south. Ben said he thought they would have fliers that could get here in a short time as soon as they got our radio message.”

“But we don’t have any radio,” Mr. Klecker said.

“Yes we do, and we can thank the flier’s lifesaving equipment for that,” Captain Eaton said.

He went to a cabinet built into the wall and pulled out an oblong box. On the top of it were the words: “SOS Automatic Transmitter.”

“You mean that was in the flier all this time and that we could have used it earlier ourselves?” Garry asked in surprise.

“Yes, you could have,” Captain Eaton replied.