Modesitt switches back to science fiction after his fantasy trilogy about the kingdom of Recluce (The Magic Engineer, p. 103, etc.), introducing an initially intriguing alternate world that is comparable in development to ours but has a substantially different history -- and where ghosts are real. Northeast Columbia (America), with its deep Dutch roots, is the quiet, hard-working, chocolate-drinking region to which former government agent Johan Eschbach has retired to teach environmental economics. But then one of his colleagues, Miranda Miller, is mysteriously murdered -- and Johan beholds her ghost at the moment of its formation. Gradually, he realizes that he has become the pivot in a power struggle between President Armstrong, Speaker Hartpence, and various foreign powers for control of new ""Babbage engine"" (computer) technology that can banish ghosts (usually they hang around) or create them to order, leaving behind a still-living and compliant zombie. So, to protect himself, Johan is forced to investigate the murder while fending off the attentions of the Spazi (secret police) and probing the affairs of his beautiful but untrustworthy lover, the singer Llysette, a spy for the Austro-Hungarian Empire. It's all marvelously inventive. But the scenario has two major flaws: the ghosts, which don't fit and are never convincingly explained; and the lack of specific historical divergence points from which Modesitt's alternate history might reasonably flow. A fairly typical performance, then, alluring yet ultimately unsatisfying.