Anne (Olivia Colman) visits her father Anthony (Anthony Hopkins) in his flat after he becomes belligerent with his recent caretaker. Anthony has dementia and constantly forgets important life events and where things are around his flat, including his watch, despite the fact that he places it in the same place every day. He tells Anne he thought his recent caretaker stole his watch and that he will never leave his flat. Anne tells Anthony she plans to leave London and move to Paris to live with her new boyfriend, which confuses Anthony since he states she's married to James. Anne tells him they've been divorced for five years and leaves.The next day, Anthony sees an unknown man Paul (Mark Gatiss), and is confused by him living in his flat. Paul states that Anthony lives with him and Anne. Anne returns from the market with chicken for dinner and appears as a different woman (Olivia Williams). This confuses Anthony to the point of frustration. Anne schedules for a new caretaker interview in his house, Laura (Imogen Poots), in which Anthony claims he was a professional dancer and that he doesn't need any living assistance. Anthony later states after she is hired that she reminds him of his other daughter Lucy, whom he hasn't talked to for months for reasons he is unaware of.Anthony is taken to a doctor by Anne and is asked about his memory; he claims he has no memory problems. Anthony tells Laura about how proud he is of his daughter Lucy, who is a painter. Laura tells him she is very sorry about Lucy's accident, to which Anthony says he's unaware what she's referring to. Laura drops the subject and moves on, giving him his medication. Over the course of the film, it is revealed that Anthony has really been living in Anne and Paul's flat for years, but believes he still lives in his private flat. The night Anne comes back with the chicken from the market, she and Paul (Rufus Sewell) have an argument over a vacation to Italy they had to cancel in order to deal with the fallout of Anthony's earlier belligerent behavior to the caretaker, and about how much Anne sacrifices for her father. Paul, this time played by Mark Gatiss, asks Anthony how long he plans to stay in their flat and annoy everyone, leading to Paul slapping Anthony to the point of crying.Anthony wakes up in his room and walks out of the flat, only to find himself in a hospital hallway. He remembers his daughter Lucy (Imogen Poots) died in a car accident at the hospital. He sees her bloody body in the hospital room then wakes up in a completely different bedroom, now in a nursing home. His nurse, Catherine (Olivia Williams), checks in on him and informs him Anne has moved to Paris with Paul and visits on occasional weekends. Another nurse, Bill (Mark Gatiss), also visits during their interaction. Anthony has an emotional breakdown over his inability to understand the world anymore and Anne's disappearance and states he wants his mother and proclaims that he is "losing his leaves." Catherine comforts him as he cries and tells him she'll take him outside to the park later that day.The film ends with a shot of leaves on a tree.