Eclipsing Binaries — E.E. "Doc" Smith

The evil conspiracy of Lady A takes a new and mysterious turn when Grand Duke Zander von Wilmenhorst - the secret Head of SOTE - is implicated in a deadly plot against the Empire. And an enemy is impersonating Jules and Yvonne d'Alembert and luring SOTE agents to their deaths.

The trails lead the Family d'Alembert out into deep space to tackle the source of this disturbing operation. And Etienne d'Alembert has his own mission - to clear the name of Zander from accusations of treason. Before long, SOTE's top agents are locked in mortal combat with some of the Empire's most powerful foes...