Based on the internationally bestselling award-winning psychological suspense novel The Marsh King’s Daughter by Karen Dionne, ‘Helena Petterier’ (Daisy Ridley) leads an ideal life with a great husband and a young daughter but she keeps secret her shocking backstory: her mother was kidnapped as a teen, and she was the product of the relationship between captive and tormentor. She lives for 12 years in a life carefully controlled by her kidnapper/father ‘Jacob,’(Ben Mendelsohn) until he is caught and sent to prison. An escape that leaves two prison guards dead forces her to confront her secret history and she becomes determined to bring down her father, who gave her all the tools she will need. He is the one called the Marsh King, the man who kept a woman and her young daughter captive in the wilderness for years. Sensing the danger this monster poses for her husband and young daughter, she vows to hunt him down.