Joe Kenmore is thrust into a hero role when an attempt to destroy the lunar jeep he and his co-pilot friend Moreau is thwarted through their speedy reaction. They rush their damaged jeep back to the civilian lunar base only to discover that an incoming rocket from Earth cannot obtain a landing beam to guide it in. The rocket has some surprise occupants and events start to escalate rapidly.

Further progress in atomic power could now come about only as a result of experiments so dangerous that they could only be carried on in an isolated space station hanging near the far side of the Moon. If these experiments succeeded, they could open the way to the stars.

To supply this space laboratory was the duty of the City on the Moon. And when Joe Kenmore, Moon colonist, realised that there were agents working actively to sabotage the city, he knew he was up against a supreme crisis of humanity – one in which his own life and those of his fellow colonists were mere pawns to be sacrificed ruthlessly by that hidden foe – unless he personally could block their super-atomic deviltry.

• Ed Emshwiller Cover at ISFDB
• City on the Moon title listing at the Internet Speculative Fiction Database