The father of the twins, Jack and Eve, dies when he and Jack are investigating a cave near their home - but was it really a rock fall as the family are told, or something altogether more sinister? Ever since industrial diggers moved in and started delving into the tunnels beneath the town of Bistombe, Jack's been having nightmares - and it seems that the diggers may have disturbed more than just the earth. Then Jack meets the historian, Eddie Doogan, and hears stories about the 'Beast of Bistombe'. When strange events start to happen in the town, and as more and more people fall victim to paranoid delusions, Jack and Eve set out to find out what really lay behind their father's death - and how it's connected to a mysterious virus in Africa . . .