This is the second novel in one of Jack Vance's science fiction series the Demon Princes, following Star King.
Kirth Gersen, while working as a police spy in the lawless Beyond, comes in possession of two papers. They have some connection to Kokor Hekkus, one of the five arch-villains Gersen has dedicated his life to bringing down. Hekkus has embarked on a galaxy-wide kidnapping spree, so Gersen heads to Interchange, a business in the Beyond that specializes in handling kidnappings and ransoms. He discovers that a young woman named Alusz Iphigenia Eperje-Tokay has "kidnapped" herself and set her ransom extraordinarily high to use Interchange to protect herself from Hekkus. Hekkus is raising that ransom with his own kidnappings. Gersen also finds Myron Patch; unlike Hekkus's other kidnap victims, he is not wealthy, merely an engineer commissioned by Hekkus to build him a "killing machine" in the form of an animal. Gersen, using one of the papers he obtained, is able to counterfeit money; he uses the fake bills to ransom both Alusz Iphigenia and Patch.
Alusz Iphigenia is from the semi-mythical planet Thamber, whose location has been lost. Patch's machine resembles a dangerous animal native to Thamber. From information Alusz Iphigenia provides, Gersen is able to find the planet. There, he discovers that Hekkus has been living a life of adventure on the semi-barbaric world under several identities, including that of Alusz Iphigenia's own fiance. He kills Hekkus and returns to civilization.
Best part of story, including ending:
Vance brings to life not one but two very different main settings.
Best scene in story:
Gersen figures out a way, while himself an Interchange "guest", to ransom himself and the others. Since Alusz Iphigenia is uninterested in the money, Gersen finds himself extremely wealthy at the expense of Interchange.
Opinion about the main character:
Gersen's resourcefulness knows no bounds. He masters both criminal and barbaric situations with equal ease.