An inter-galactic waif, Thorby, was sold at a slave auction to Baslim the Cripple. Then, in accordance with his instructions the boy undertook a search for his ancestry on board the space ship Sisu. The mystery of his parentage tormented Thorby through all of the adventures he met in the free wheeling trading enterprises of the ship he called home. But final identification posed a dilemma. Thorby discovered that he was heir to the interstellar Rudbeck corporation. Since the disappearance of his parents control had fallen into the unscrupulous hands of a man engaged in slave trade. Sometimes satirical, probingly provocative, this is a characteristic Heinlein off-the-ground mirage, with the protagonist encountering the values of a free society, weighing the worth of the individual. Margaret Mader, the bustling lady anthropologist who proves a friend to Thorby (her resemblance to Margaret Mead seems more than coincidental) is a typical Heinlein touch in this synthesis of reality-unreality.