Roger Korby, described as the "Pasteur of archaeological medicine" has built a reputation recovering the knowledge of dead alien civilizations, until five years ago when his entire expedition was lost on the frozen world Exo III. Or was it? When Enterprise assumes orbit, someone using Korby's voice responds to their hails. It seems Korby discovered that the civilization of Exo fled their ice age by going underground. He has uncovered some of their science, including their machinery for producing hardy androids - and for transferring a consciousness into such a machine. And he has plans for that technology. Ambitions, sinister plans...

Enterprise stops at the Tantalus penal colony to deliver drugs and collect research materials. Except that the research materials box contains a dangerous madman, Simon van Gelder - the former director of the colony. Kirk and psychiatrist Helen Noel beam down to speak with Tristan Adams, to learn what happened to van Gelder. It seems Dr. van Gelder was the victim of a new device, a neural neutralizer. But was what happened really an accident, or something more sinister?