Thorby is a young, defiant slave boy recently arrived at the planet Jubbul's capital Jubbulpore, where he is purchased by an old beggar, Baslim the Cripple, for a trivial sum and taken to the beggar's surprisingly well-furnished underground home. Thereafter Baslim treats the boy as a son, teaching him not only the trade of begging, but also mathematics, history, and several languages, while sending Thorby on errands all over the city, carefully passing along information and keeping track of the comings and goings of starships, so that Thorby realizes that his foster father is gathering intelligence, particularly on the slave trade. In addition, Baslim has 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. When Baslim is captured by the local authorities and commits suicide, Thorby and local innkeeper 'Mother Shaum' convey the message to Captain Krausa of the starship Sisu . Because the 'Free Trader' society to whom Krausa belongs owes a debt to Baslim for the rescue of one of their crews from a slave trader, the captain takes Thorby aboard the 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, in which position Thorby destroys a pirate craft. His immediate superior, a young woman named Mata, begins to view him as a suitable husband—something forbidden by the Free Trader's customs, and she is transferred to another ship.
Thorby is again transferred when the captain, against the wishes of his wife, the executive officer and head of the clan (who wants to use Thorby's connection to Baslim to enhance Sisu 's prestige), obeys Baslim's last wish, entrusting the boy to a military cruiser and asking its captain to assist Thorby in finding his own people. In order to implement a background search without having to pay the immense cost, Thorby is 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 including one of the largest starship-manufacturing companies and the entire city of Rudbek (formerly Jackson Hole, Wyoming). In his absence, the business is run by a relative by marriage, "Uncle" John Weemsby, who encourages his stepdaughter Leda to guide Thorby in adjustment to his new situation while secretly scheming to block Thorby's growing interest and interference in the company.
Thorby, investigating his parents' disappearance and his capture and sale by slavers, 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 further investigation, Thorby seeks legal help and launches a proxy fight, which he unexpectedly wins when Leda votes her shares in his favor. He fires Weemsby and assumes full control of the firm. When Thorby realizes that it will take a lifetime to remove Rudbek and Associates from the slave trade, he reluctantly abandons his dream of imitating Baslim as a member of 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.