John Gordon is a regular insurance agent. All of a sudden he starts hearing a voice in his head calling him by name. After few nights, he decides to answer the voice, and learns that a man named Zart Arn, 2000 centuries from the future is communicating with him. Zart is a Prince and a scientist who studies the past and wants to switch minds with Gordon. Gordon agrees and wakes up in Zart's laboratory in the future. After about a week in the company of Zart's assistants, Gordon learns the language and some of the history of the times. Then, there is an abduction attempt. He is rescued and brought to Zart's home planet - the capital of the Galactic Empire. Because he promised Zart that he will not reveal his true identity, Gordon is immersed in the political power-play, as the son of the emperor. He falls in love with a princess, bound to marry Zart for political reasons. He and the princess are kidnapped and brought to the leader of the attackers, who kill the emperor. In his attempt to learn the secret of a super weapon, "Destroyer", which only the emperor, and his sons know, the leader learns that Gordon is not Zart.
After Gordon's escape, an attack is orchistrated and Zart has to take the lead. He is forced to use the Destroyer and wins the war. Only then he is able to return to the laboratory and switch his mind back with the real Zart Arn.
This report prepared by irina