After the death of Malcolm Kinniburgh, who had previously kept the Thistlebone legend alive, the local Harrowvale constabulary find clues that lead them to investigate the abandoned film production of a 1970s folk horror film, The Dule Tree. Based on a harrowing account from the seventeen hundreds where thirteen innocent women and one man were hanged during the witch trials, the film itself ran into production problems, the source of which has remained a mystery for fifty years.