Harvey Shine (played by Dustin Hoffman) is a divorced, struggling jingle-writer who is invited to his daughter's wedding in London. However, upon arriving at the airport, he finds out that he has missed his flight to New York due to a delay at security. Harvey is devastated that he will miss his daughter's big day and also loses his job as a result of missing the flight.
While drowning his sorrows at the airport bar, he meets Kate (played by Emma Thompson), a middle-aged British government worker who is stuck in a monotonous routine of work, phone calls from her mother, and blind dates. The two start talking and find that they have a connection, despite their initial reluctance towards each other.
Harvey agrees to take Kate to her niece's wedding the next day as her date, and they spend the entire day together, exploring London and enjoying each other's company. As they spend more time together, they begin to open up to each other and reveal their personal struggles, including Harvey's relationship with his daughter and Kate's fear of being alone.
Despite the time constraints of the trip and the challenges that come their way, including a conflict with Harvey's daughter, the two continue to grow closer and eventually fall in love. In the end, Harvey decides to stay in London with Kate to start a new chapter in his life, leaving behind his old job and his previous life.