Imperial Earth was published as the middle book of a three-novel contract that also included Rendezvous with Rama (1973) and The Fountains of Paradise (1979). Although they were parts of a multibook contract involving more money than ever previously paid in the science-fiction field, each of the three works is a stand-alone novel.
In Imperial Earth, Duncan Makenzie is a key figure in the administration of the small but thriving world of Titan, Saturns largest moon. He shares this responsibility with his older “brothers”: Colin Makenzie, who acts as Duncan’s “father,” and Malcolm Makenzie, the space pioneer from whom both Duncan and Colin were cloned.
As the novel opens, Duncan is preparing to travel to Earth, where he will take part in the United States quincentennial celebration, solidify his familys political position, and arrange to bring a fourth-generation Makenzie back to Titan. Duncan also hopes to reacquaint himself with a woman named Calindy who had visited Titan fifteen years earlier. Both Duncan and Karl Helmer, the son of the Makenzies biggest rival for power on Titan and also an object of Duncans affection, fell in love with Calindy during that time, but for Karl the relationship had led to an emotional breakdown.
Although busy with diplomatic duties and new experiences on an Earth that is utterly alien to him, Duncan learns that someone is selling large quantities of Titanite, a rare mineral from his home world. Investigation reveals that Karl secretly arrived on Earth some time before Duncan and is selling Titanite with Calindys help, but his purpose is unclear. When Duncan confronts Karl, an accident sends Karl plunging to his death. It is only from notes in Karls computer and sketchbook that Duncan discovers Karl had hoped to finance a Communications with Extraterrestrial Intelligence (CETI) project on an unprecedented scale. After wrapping up his diplomatic obligations and arrangements for Karl’s estate, Duncan returns to Titan with the cloned baby he came for—but it is a clone of Karl, not of Duncan.