When Tom Ronstadt (John Simm) finds himself sacked from his job and dumped by his lover, with no-one else to turn to he decides to return home for the first time in 18 years. Having fled after a violent and unforgiving incident by his father all those years ago, he is forced to confront his past. Arriving home he finds his father, Sam (Jim Broadbent), in the grip of Alzheimer's being cared for by his sister, Nancy (Olivia Colman). With Tom's arrival she decides to take advantage and have a break, leaving him to care for his father alone. Using the time together, he begins to investigate the circumstances that drove him away all those years ago. All he can remember from that brutal beating was the name Metzler... flashing back and forth to that fateful night, can Tom help Sam remember anything to piece together the terrible secret?