Secrets from the past emerge to threaten archaeologist Nina Wilde and her husband, former SAS soldier Eddie Chase, when a Viking runestone is stolen by a murderous gang of raiders. The stone holds the key to an ancient evil concealed in one of Norse mythology's holiest places: Valhalla. Travelling to Sweden, Eddie and Nina find themselves in a race against time to locate the legendary hall of the Viking warriors - before rival powers claim its deadly contents for themselves. It is a quest that will force Eddie to revisit a dark chapter from his mercenary days that he has kept hidden from everyone including his wife. Only Nina and Eddie can prevent the unleashing of primordial terror from the depths of the earth. But even if they succeed, will the cost be greater than either of them could have ever imagined?