In 1950s England, Mr Stevens (Anthony Hopkins), the butler of Darlington Hall, receives a letter from Miss Kenton (Emma Thompson), who worked with him as housekeeper during the years prior to the Second World War. Twenty years later, Lord Darlington (James Fox) has died and his stately country manor has been sold to a retired American Congressman, Mr. Lewis (Christopher Reeve). Kenton reveals that her marriage has failed and that she is nostalgic for the days when she worked at the house. Stevens (now one of the few remaining servants from the Darlington era) goes to visit Miss Kenton, ostensibly to persuade her to return to service.
The film flashes back to Kenton's arrival as housekeeper. At the time, Darlington Hall was frequented by many politicians of the interwar period, men who decided important affairs of state while there. Stevens, loyal and perfectionistic, calm and efficient, had to manage the household so that the servants seemed almost invisible, and he took great pride in his skills and his profession. He clashed with Miss Kenton, his equal in the household hierarchy, but displayed only understated irritation with her and others. Indeed, his utter focus and emotional repression were most fully displayed when his own father, also an employee, was dying; Stevens continued his duties without pause.
Miss Kenton was equally efficient and strong-willed but warmer and less repressed. Relations between the two eventually warmed and Kenton even teased Stevens. It becomes clear that she had fallen in love with him, and perhaps he with her, though his feelings are left ambiguous. She tried to break through the wall, but Stevens' coldness was too formidable. Finally, she struck up a relationship with another man and married him, leaving the house just before the outbreak of World War II. Before her departure, she insulted Stevens, clearly out of distress that he had never expressed any emotional interest in her, but he still refused to be moved. When she cried in frustration, the only response he could muster was to call her attention to a domestic task.
Lord Darlington used his influence to broker the policy of appeasement towards Nazi Germany. He irritated Congressman Lewis, one of the dignitaries at a conference, who argued in favour of the foreign policy being conducted by "professionals" rather than by "gentlemen amateurs". After reading the work of Houston Stewart Chamberlain, Lord Darlington commanded that two German-Jewish maids should be dismissed, considering their employment inappropriate. Stevens carried out the order but Miss Kenton almost resigned in protest, fearing that the girls would have to return to Germany; her own need for employment caused her to avoid following through. Darlington later regretted his decision and asked Stevens to reinstate the maids, but they could not be located.
Darlington died a broken man, his reputation destroyed after he had been denounced a traitor in the Daily Mail. When asked about his former employer, Stevens at first denies having served or even met him but later admits to having served him. He recognises his former master's failings and indicates that he has regrets about his own life, as does Miss Kenton (now Mrs. Benn). However, Kenton declines Stevens' offer to return to Darlington Hall, announcing instead that she wants to remain with her husband, since their daughter is soon to present them with a grandchild. After the meeting, Stevens departs for Darlington Hall in a downpour of rain. Kenton cries, while Stevens, still unable to demonstrate any feeling, simply raises his hat.
The film's final scene shows Stevens making the final preparations to Darlington Hall in preparation for the arrival of Congressman Lewis' family. As the two men enter the banquet hall, where a table tennis table now lies, Congressman Lewis reflects on the banquet that he attended in this room in 1935 and admits embarrassment over his comments. He asks Stevens if he remembers the comments, to which Stevens replies that he was too busy serving. Symbolically, a pigeon then flies into the room through the fireplace and becomes trapped in the hall. The two men eventually coax it out a window and it flees to freedom, leaving Stevens and Darlington Hall behind.