Citizen of the Galaxy is a science fiction novel by Robert A. Heinlein, originally serialized in Astounding Science Fiction (September, October, November, December 1957) and published in hardcover in 1957 as one of the Heinlein juveniles by Scribner's. Influenced by Rudyard Kipling's Kim, the novel, like many of Heinlein's, is also influenced by the author's background in and nostalgia for the U.S. Navy.
Baslim treats the boy as he would his son, teaching him not only the honorable trade of begging, but also mathematics, history, and several languages. He sends Thorby on errands all over the city, carefully passing along information and keeping track of the comings and goings of ships. Thorby realizes that "Pop" is more than a simple beggar; he is gathering intelligence, particularly on the slave trade. Baslim makes Thorby memorize a contingency plan and a message to deliver to one of five starship captains in the event of Baslim's arrest or death.
One day, coming back from an errand gone awry, Thorby finds out that the old man has been captured in a police raid. Thorby realizes he has become a hunted fugitive. He knows his "friends" would gladly turn him in for the reward offered, so he turns to Mother Shaum, a local "taproom" owner whom Baslim trusted. He finds out from her that Baslim foiled his captors by taking poison before he could be tortured for what he knew. She also tells Thorby that Baslim's head is displayed impaled on a pike, but still wearing a defiant grin.
As luck would have it, one of the men on Baslim's list is in port. At Thorby's insistence, Mother Shaum arranges a meeting. The Free Trader listens to Thorby's memorized message, which is in a language Thorby does not understand. The Free Traders owe a great debt to Baslim and the captain honors it, smuggling Thorby aboard the starship Sisu at great risk to himself and his clan.
Thorby is adopted by the captain (thereby gaining considerable shipboard social status) and adjusts to the insular, clannish, matriarchal culture of the traders. The advanced education provided by Baslim and the fast reflexes of youth make him an ideal fire controlman. When they are attacked by a pirate, Thorby destroys it with a nuclear missile. His immediate superior, a young woman named Mata, begins to view him as a suitable husband, but the customs of the Free Traders forbid this. To avoid trouble, she is transferred to another ship.
Thorby is soon uprooted once more. Defying the wishes of his wife, the executive officer and effective head of the clan, the captain obeys Baslim's last wish. He turns the boy over to a Hegemonic Guard cruiser and asks its captain to assist Thorby in finding his real identity and family as a final favor to the man the Guard knows as Colonel Richard Baslim. In order to implement a background search without having to pay the immense cost, Thorby is summarily enlisted in the military service of the Terran Hegemony, the dominant military power in the galaxy.
Thorby is ultimately identified as Thor Bradley Rudbek, the long-lost heir of a very powerful family and a substantial shareholder in Rudbek and Associates, a large, sprawling interstellar business empire. This includes one of the largest starship manufacturing companies and the entire city of Rudbek (formerly Jackson Hole, Wyoming). In his absence, the business had been run by a relative by marriage, "Uncle" John Weemsby. Weemsby encourages his stepdaughter Leda to help Thorby get his bearings and enjoy his newfound wealth, while Weemsby secretly tries to block Thorby's growing interest and interference in the company.
Thorby digs into the mystery of his parents' disappearance and his capture and sale by slavers two decades earlier. He discovers that their space yacht was lost while his father was on an inspection tour of his far-flung business empire. He comes to suspect that his parents were eliminated to prevent the discovery that some portions of Rudbek and Associates were secretly profiting from the slave trade.
When Weemsby quashes his attempts to find out more, Thorby secretly seeks legal help and launches a proxy fight, barely winning when Leda unexpectedly votes her shares in his favor. He fires Weemsby and assumes full control of the firm. When he realizes that it will take a lifetime to clean up the mess he finds, he reluctantly abandons his dream of following in Baslim's footsteps and enlisting in the elite anti-slaver "X" Corps of the Hegemonic Guard. Knowing that "a person can't run out on his responsibilities", he resolves to fight the slave trade as the head of Rudbek and Associates, Ltd.
Other authors reviewing the book argue that the argument against slavery is actually a powerful statement about the need for continuing education. As in many of Heinlein's books, the principal character is portrayed over time, beginning in relative ignorance, learning from experience, receiving the benefits of education, and using that education to resolve subsequent problems in his / her own life and that of those around them.
Finally, Citizen of the Galaxy makes a compelling statement about the cost of honor, and about loyalty.