When Wilbur, portrayed by Adrian Rawlins, leaves the hospital after another suicide attempt, the staff implore his brother Harbour to allow him to stay with him. The brothers settle into their childhood apartment, situated above the bookshop left to them by their father. While Wilbur is disinterested in running the family business and finds work at a nursery, Harbour manages the shop. It’s there that he meets Alice, played by Shirley Henderson, a hospital cleaner who frequently brings him books she finds at her job. After she loses her job for tardiness, Alice visits Harbour to explain her absence.
Taking a tip from Wilbur about winning over women, Harbour boldly proposes to Alice during a dinner at an Asian restaurant, which also gives Wilbur the chance to meet Sophie, Alice’s former colleague. Although there's some playful flirting, Wilbur awkwardly dismisses Sophie when she licks his ear. Later, in a dark turn, he retreats to the bathroom and attempts to end his life. However, Harbour arrives just in time to prevent a tragedy with the help of Alice, who applies towels to stem Wilbur's bleeding. During a conversation with Alice, Harbour reveals that Wilbur carries the guilt of their mother's death.
As Wilbur attempts to navigate life post-hospital, he encounters a nurse named Moira who becomes infatuated with him. In a moment lacking reciprocity, he brushes her advances aside. Meanwhile, Harbour receives troubling news about his health but is reluctant to stay in the hospital, wishing to focus on his new family instead. The four of them—Wilbur, Harbour, Alice, and little Mary—try to build a life together, leading to a comedic yet touching birthday gathering marred by hiccups, including Wilbur throwing up on a little girl's dress.
Tension builds as Wilbur makes a desperate attempt to leap from a building but ultimately realizes he is not ready to leave life behind. When he tries to apologize to Alice for their previous kiss, they find themselves swept back into a moment of affection. Meanwhile, Harbour wrestles with his terminal illness, burdened by how to convey the severity of his situation to those he loves.
To stave off his feelings for Alice, Wilbur awkwardly pursues a relationship with Moira. However, during a family meal, Moira suggests dietary changes to aid Harbour’s chemotherapy, further igniting Alice’s frustrations at Harbour for avoiding treatment. Concerned about Wilbur's wellbeing, Alice spends the night in the hospital with Harbour, while Wilbur, realizing that he must care for Mary, decides against suicide.
Eventually, Wilbur steps up to manage the bookshop in place of Harbour, whose health declines further. With the gravity of the situation weighing upon them, Harbour is granted the chance to celebrate Christmas at the shop. As he tucks Mary into bed that night, she innocently suggests that Wilbur will be sleeping with Alice, leading to a misunderstanding about their relationships.
In a heartbreaking conclusion, Harbour decides to take matters into his own hands, overdosing in his hospital room after making a heartfelt request of Wilbur to look after Alice and Mary. The film poignantly ends with Wilbur, Alice, and Mary standing solemnly at Harbour’s grave, united in their grief and memories.