Medusa — an experimental spaceship developed by the Advanced Research Department of St Oscar's University. Missing since it was launched, presumed lost in the wars, it was a project so secret that it has never been declassified.

Now, twenty years on, Medusa is coming home.

After one of the investigation team dies suspiciously, Professor Bernice Summerfield is assigned to help discover what went wrong. But to do so she must solve a riddle. What is the strange link between the original crew and the team now on board the drifting ship? And why do their ghosts still haunt Medusa?