The Doctor takes Peri to the Memory Farm - a state of the art space station where hidden memories can by harvested and analysed. To their surprise, they find the station in lock-down and ill its resources dedicated to probing the memories of an elderly man. Garius Moro may, or may not, have been responsible for the deaths of billions of people many years ago, but he simply can't remember.
This book is part of the Doctor Who: Big Finish Monthly Adventures Audio Books series and is book #87 in the series.