A 4000-year-old body is found preserved in an Irish peat bog, in Cashel, in Ireland's midlands. To scientists and historians, it could offer brand new clues to solve an ancient mystery: the hundreds of bodies found mummified in the boglands of Northern Europe. An international team of experts assemble to investigate this new find, led by Ned Kelly of the National Museum of Ireland. Ned is a veteran archaeologist, and has previously investigated some of Ireland's most famous bog bodies. Now, will 'Cashel Man' help prove his theory these Irish victims were ancient kings? And what clues can the bog bodies of Europe offer to explain our ancestors' most macabre tradition, ritual murder? Meanwhile, that question could be answered by the bog itself. New science has found clues to suggest these deaths may be explained by prehistoric climate change.