It is the near future. Axel, a computer scientist, with broad, mechanically-inclined hobbies, is working on a prototype matter transmitter. It is erratic and, in an instant, he finds his consciousness has been transmitted across space. It has been received into the brain of a young, male humanoid immediately following the latters brain-death from a traumatic wound; one that has not, however, left any long-term organic injuries: Axel of Earth has become Lexar of Nandroth.
Lexars race are called the Androthi. Their world has some geophysical similarities to Earth, and some similarity of life forms but with notable exceptions. The civilisations of the Androthi are roughly on the same technological level as 14th century Europe and Asia. Their overwhelming problem is that their world has been invaded by self-replicating robots, the mekkans, which have a highly advanced and to living creatures deadly technology.
The mekkans are relatively few in number. They require, for their power and construction, minerals that they cannot easily find and mine. To obtain them, they have set about subjugating Nandroth and enslaving the Androthi, either by direct force or by fomenting internecine warfare. Their ultimate intention is to refuel their nuclear-powered space craft and continue their conquest of living worlds in the universe.
Axel-Lexars self-appointed task is to get his fellow Androthi to accept who and what he is, and to get them to help him create, with what resources are available, strategies to defeat the mekkans. Above all, he wants to destroy the mekkans ability to threaten intelligent life forms on other worlds.
The work deals, inter alia, with the nature of the linguistic problems faced by Axel on his becoming Lexar and the means by which he attempts to transform the local technology. He seeks to exploit special features of mekkan engineering and their rigid social structure, in order to subvert their seemingly unassailable power. But, in the meantime, there are defences to organise against the mekkans highly advanced weapons, and battles to be fought against other Androthi nations who have become the mekkans allies.
To complicate his new life, he finds that Lexar is betrothed to the teenage daughter of the local Lord. She is a highly intelligent, independent and passionate individual, at first disbelieving, then suspicious and finally jealously protective.