Far down into the earth goes a gleaming metal sphere whose passengers are deadly enemies.
Excerpt
A strange spherical monster stood in the moonlight on the silent Mojave Desert. In the ghostly gray of the sand and sage and Joshua trees its metal hide glimmered dully?an amazing object to be found on that lonely spot. But there was only pride and anticipation in the eyes of the three people who stood a little way off, looking at it. For they had constructed the strange sphere, and were soon going to entrust their lives to it.
"Professor," said one of them, a young man with a cheerful face and a likable grin, "let's go down now! There's no use waiting till to-morrow. It's always dark down there, whether it's day or night up here. Everything is ready."
The white-haired Professor David Guinness smiled tolerantly at the speaker, his partner, Phil Holmes. "I'm kind of eager to be off, myself," he admitted. He turned to the third person in the little group, a dark-haired girl. "What do you say, Sue?"
"Oh, let's, Father!" came the quick reply. "We'd never be able to sleep to-night, anyway. As Phil says, everything is ready."
"Well, I guess that settles it," Professor Guinness said to the eager young man.