Orphans of the Sky is a compelling science fiction novel that combines two novelettes: "Universe" and "Common Sense", both originally published in 1941. The story unfolds within the confines of a massive spaceship, known simply as the Ship.

Hugh, the protagonist, has always been taught that the Ship is on a sacred voyage to the distant star, Centaurus. This journey is believed to be a metaphor for achieving spiritual enlightenment. To the inhabitants, the Ship represents the entirety of existence, a seemingly endless expanse of metal corridors.

The Ship's universe is maintained by the sacred Convertor, ensuring that lights shine and air flows. Yet, lurking in the upper reaches of the Ship are the muties, grotesque figures thought to be either evil beings or a divine population control mechanism.

When Hugh is captured by the muties, he encounters their leader, Joe-Jim, a unique individual with two heads on one body. Through this encounter, Hugh learns the startling truth about the Ship's true mission among the stars. The question remains: Can he convince his people of this truth before it's too late? Can he become the one to navigate the Ship?