This is the last of Heinlein’s “juveniles” or novels for young readers, and my favorite.
High school student Kip Russell is not quite sure what he wants to do with his life, but getting into space must be a part of it. Civilian space travel is available to the very rich, but way beyond the reach of Kip and his family. His father suggests he enter a contest offered by a soap company with a trip into space as the first prize for the best slogan for their soap, and Kip goes after it with enthusiasm, finding ways to sell soap to everyone in town and get the wrappers to send in with slogans, hundreds of them. He does not win the trip, but gets a lesser prize, a decomissioned but real space suit. Before he goes off to college, Kip makes it his summer project to get the suit into working order, using his machine shop skills to restore the suit and stocking it with missing items like air bottles and a radio from his summer job earnings. With the suit complete, he takes it for a practice run outside his home, calling on the radio to an imaginary ship. To his surprise and shock, he’s answered by the voice of a girl, and presently two unidentified flying objects, alien space ships, land in the field near him. A girl jumps out with some kind of small companion, but before Kip can get to them, all three are captured and knocked senseless by some kind of paralysis beam.
Kip wakes up in a cell with the girl, Peewee, who is much younger than he expected, and learns they’re prisoners of alien invaders in their hidden base on the moon. Kip and Peewee plan a daring escape, and with them will go a different friendly alien Peewee calls The Mother Thing. She is a kind of space cop, but also a prisoner. There are many problems to overcome in their escape, the worst being having enough breathable air to get them to a government base many miles away, but the three prisoners get free and begin their deadly march across the airless, mountainous moon terrain, not knowing if they will die in the attempt.
Heinlein got everything right in this one. He knew a lot about actual pressure suits, having worked on them for the government, and Kip’s restoration of the suit is completely believable and draws you right into the story. The characters are appealing without being preachy, and the plot is full of surprises that moves the narrative from the Moon, to Pluto, to a distant planet far from Earth. Our planet is eventually threatened with complete destruction and put on trial with only Kip and Peewee to defend it. Great story, never a dull moment, memorable characters, and full of fine ideas. Highly recommended.