Peggy Jenkins and her teenage son, Samson, live on a remote stretch of canal in the Midlands. She is a writer and he is a schoolboy. Together, they battle against the hardness and manipulation of the man they live with. To the outside world he is a husband and father. To them, he is a captor. Their lives are tightly controlled; if any perceived threat appears, their mooring is moved further down the canal, further away from civilisation. Until the day when the power suddenly shifts, and nothing can be the same again.