In a German cave in 1872, an amateur archeologist made a grisly discovery. A mass grave containing the bodies of one man and over forty women, some of whom had been beheaded. Was this the site of one of the largest human sacrifices in the Celtic world? Uncover the unknown history of the Celts, a people who left no written record but communicated their past through song and story, who came from central Europe and spread across the continent.