The novel tells, in first-person narration, the story of Stevens, an English butler who has dedicated his life to the loyal service of Lord Darlington (who is recently deceased, and whom Stevens describes in increasing detail in flashbacks). The novel begins in the late 1950s, with Stevens receiving a letter from a former colleague, the housekeeper Miss Kenton, describing her married life, which Stevens believes hints at an unhappy marriage.

Stevens' receipt of the letter coincides with his opportunity to revisit this once-cherished relationship, if only under the guise of investigating the possibility of her re-employment. Stevens' new employer, a wealthy American named Mr. Farraday, encourages Stevens to borrow his car to take a well-earned break—a "motoring trip". Stevens takes the opportunity to arrange to meet with Miss Kenton (now a Mrs. Benn) in Cornwall, where she had moved to live with her husband.

Upon setting out, Stevens reflects on his unshakable loyalty to Lord Darlington, who had hosted lavish meetings between German sympathizers and English aristocrats in an effort to influence international affairs in the years leading up to World War II; on the meaning of the term "dignity" and what constitutes a great butler; and also on his relationship with his late father, like him a "no-nonsense" man who dedicated his life to service. Ultimately, Stevens is forced to ponder Lord Darlington's character and reputation, as well as the true nature of his relationship with Miss Kenton. As the book progresses, evidence mounts of Miss Kenton's and Stevens' past mutual attraction and affection.

While they worked together during the years leading up to the Second World War, Stevens and Miss Kenton failed to admit their true feelings toward one other. Their conversations as recollected by Stevens show a professional friendship which at times came close to blossoming into romance, but this was evidently a line that neither dared cross. Stevens in particular never yielded, even when Miss Kenton tried to draw closer to him.

When they finally meet again, Mrs. Benn, having been married now for more than twenty years, admits to wondering if she made a mistake in marrying, but says she has come to love her husband and is looking forward to the birth of their first grandchild. Stevens later muses over lost opportunities, both with Miss Kenton and regarding his decades of selfless service to Lord Darlington, who may not have been worthy of his unquestioning fealty. At the end of the novel, Stevens instead focuses on the titular "remains of the day", referring to his future service with Mr. Farraday and what is left of his own life.