It's a gruesome mass murder no one knew about until a 2011 excavation revealed the sinister secret. Discover the story of a pre-Viking warrior tribe that was massacred in Swedish ringfort Sandby Borg and left to rot where they fell. Follow investigators as they piece together what happened 1,500 years ago, using cutting-edge modern forensic analysis. It's a tale of betrayal and power struggles that has haunted the Baltic island of Oland for centuries.