Planet of Treachery — E.E. "Doc" Smith

Classic space opera adventure, Book #7 in the "Family D'Alembert" series. For centuries, the planet Gastonia has been a planet of exile, an escape-proof prison world for the worst sorts of traitors. But now, it seems, prisoners are indeed escaping, and all evidence points to the sinister, all-knowing conspiracy that continues to shadow the Throne. The d'Alemberts must infiltrate this world of traitors - and they must do it without a safety net, because if they fail they themselves will be trapped on this inhospitable world.