It's the week before Halloween. Char's bedridden mother, Angela, has mysteriously gone missing. All that remains is her abandoned car parked in the middle of a field. When Angela returns home to their North Dublin estate the following evening without explanation, it becomes clear to Char and her grandmother, Rita, that something is amiss. She might look and sound the same, but Angela's behavior has become increasingly erratic and frightening, as if she has been replaced by a malevolent force. As Halloween approaches, a night steeped in ancient Irish myth and legend, Char must unearth the dark secrets of her family in order to uncover the truth behind her mother's disappearance and save her, even if it means potentially losing her forever.