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The veteran crew are captain Bykov, flight engineer Zhilin, navigator Krutikov and the inspector-general Yurkovsky. At each stop, including observatories, mines and the asteroid prospectors of Bamberga, Yura sees a different version of what work in space does to people. The voyage ends with Yurkovsky and Krutikov dying in Saturn's rings, and Yura arrives having learned from the men rather than from the romance of space.
On Bamberga, prospectors in a privately run mine hunt valuable 'vacuum pearls' and live in drunkenness, greed and petty cruelty despite the advanced technology around them. The book argues that moving humans to a new frontier carries their old motives along unchanged. Whether a place becomes decent depends on why people work there, not on how far out or how advanced it is.
Zhilin, a skilled spaceman, concludes that the hard, unfinished work of the future is raising people and changing how they relate to one another, not conquering planets. Seeing expansion this way treats rockets and mines as secondary. Progress is measured by what kind of person the society produces, and the most important job becomes teaching and shaping people on Earth.
The veterans are not adventurers. They are tired, ironic professionals doing inspections, repairs and cargo runs, and their courage shows up as doing dangerous work carefully and without fuss. Yura has to trade his romantic idea of space for respect for daily craft. The book treats maturity as the moment when meaningful work stops looking glamorous and still feels worth doing.