The film 'Half-Hanged Mary' follows Mia Summers, a university journalism student, who becomes engrossed in the story of a 19th-century alleged witch and the mysterious case of a young girl, Brooke Evans. As Mia investigates Brooke's haunting experiences attributed to the witch, she faces increasing danger, culminating in her mysterious disappearance. The narrative intertwines themes of academia, obsession, and supernatural elements as Mia's curiosity leads her into a chilling investigation.