Harvey Shine, played by Dustin Hoffman, is a jingle writer in the bustling world of Manhattan television commercials. Despite his undeniable talent, Harvey finds himself stuck in a job that falls far short of his dreams of being a jazz composer and pianist. Frustrated by his boss's lack of appreciation for his latest work, he embarks on a trip to London for his daughter Susan's wedding, a journey that his boss suggests he extend. However, motivated by a looming client meeting, Harvey opts to return to New York sooner than his boss recommends.
On the flight, he attempts to strike up a conversation with a fellow passenger, only to be met with indifference. This encounter adds to his feelings of inadequacy, portraying him as a man down on his luck. Across the pond, we meet Kate Walker, portrayed by Emma Thompson, a single woman grappling with her own challenges and her mother's anxieties regarding a new neighbor. Kate's relationship with her mother is tested as she tries to manage her mother's fears about the seemingly sinister Polish man next door.
Upon landing at Heathrow Airport, Harvey's first encounter is with Kate, who is collecting passenger statistics. His impatience leads him to brusquely dismiss her inquiries, highlighting his eagerness to settle into his hotel. However, he quickly discovers that he is alone at the hotel while his ex-wife Jean has arranged a house for the family. Misfortune continues to follow Harvey as he navigates the awkward dynamics of the wedding rehearsal dinner, feeling overshadowed by Jean's new husband, Brian, who assumes the role of father of the bride. A particularly hurtful moment occurs during the toast, when Brian recalls fond family memories and the stepson-to-be affectionately calls him "Dad."
Back in London, Kate fumbles through her own blind date arranged by a well-meaning coworker, only to end up feeling out of place and unloved. Her overbearing mother looms in the background, convinced of the neighbor's criminality due to his unusual activities. When Harvey attends his daughter’s wedding the next day, he arrives late, only to find that he has missed taking the flight back to New York and, more devastatingly, he gets fired for his tardiness.
As Harvey drowns his sorrows at the airport bar, he exchanges barbs with Kate, who notices his demeanor, leading to an unexpected connection over shared meals. Through humorous interactions, they gradually open up to one another. Harvey's wistful gaze as Kate departs propels him to follow her, and he asks to escort her to a writing class, further solidifying their budding bond.
As the two walk along the scenic River Thames to attend Susan's wedding reception, fate intervenes when Harvey becomes determined to attend the event, convincing Kate to join him. The reception culminates with Harvey reclaiming his position in Susan’s life by delivering a heartfelt toast that resonates with his daughter while simultaneously charming Kate.
Their night of connection extends into dawn, and while excitement lingers for their next meeting, Harvey suffers a medical emergency that leads to him being hospitalized. Despite his attempts to contact Kate once he is released, she is left waiting alone at the cafe, heartbroken over his absence.
In a twist of fate, Harvey learns from his ex-boss that he is welcomed back to work, but he finally decides to prioritize his newfound aspirations over the confines of a career he once held dear. Meanwhile, Kate's perception of her neighbor shifts from fear to understanding upon discovering that he is merely a meat smoker.
When Harvey rushes to the airport in a bid to win Kate back, he faces a series of misunderstandings but remains persistent. After finally revealing the truth about his absence, their cautious hearts begin to soften towards each other. Kate, battling with past disappointments, ultimately accepts Harvey's invitation to explore a future together.
As they contribute to the whimsical charm of London, the story sprinkles moments of levity and warmth amidst the challenges of forging new relationships, with the credits rolling over a heartwarming conclusion where Kate’s mother bravely ventures to meet the misunderstood neighbor, illustrating the theme of connection and understanding that permeates the film.
