Boris Yelnikoff is a cynical, misanthropic chess instructor, once a professor of quantum mechanics at Columbia. After his divorce, he isolates himself, interacting only with a few friends and students, often looking down on anyone who doesn't match his intellectual standards. A quirky habit of his is frequently washing his hands while cheerfully singing "Happy Birthday."
One evening, Boris discovers a young woman named Melody on his doorstep, who is somewhat simple-minded and just 21 years old. Though initially reluctant, he helps her and soon hears her story of escaping her strict, fundamentalist upbringing in Mississippi. After some hesitation, he allows her to stay the night, leading to a unique relationship where she develops a crush on him, despite their obvious differences in age and background.
Melody secures a job as a dog walker and meets Perry Singleton, agreeing to a date with him. After returning home, she confides in Boris that she didn't care for Perry because he seemed to love life too much. This revelation sparks a realization in Boris: he's fallen in love with her, and they eventually get married.
Fast forward a year, and Melody's mother, Marietta, finds her, believing that her daughter has been abducted. Marietta reveals her own marital woes, having been left by her husband John after losing money in the stock market. Their lunch together introduces her to Boris, who fails to impress her, causing her to push Melody to consider ending her marriage. During this outing, they meet Boris's friend, Leo, who takes a shine to Marietta. When Marietta steps away, a young man named Randy Lee James inquires after Melody, and Marietta plots to introduce Randy as a potential suitor for her daughter.
As the weeks go by, Marietta undergoes a transformation, delving into artistic photography and forging an open relationship with Leo and his partner, Morgenstern. However, her attitude toward Boris remains negative, and she continues to manipulate situations to promote a romance between Melody and Randy. In one of these orchestrated meetings, Randy successfully leads Melody to reveal her dissatisfaction with her marriage. This initiates an affair between the two, complicating matters further.
John, still regretful, tries to reunite his family, but as he attends Marietta's photography opening, he realizes how much she has changed in New York. Struggling with his feelings, he drowns his sorrows in a bar and ends up meeting Howard, a recently divorced gay man, and confronts his own sexuality.
In a heartbreaking confession, Melody reveals to Boris her love for Randy, which sends him into a spiral of despair. In an erratic moment, he jumps out of a window, inadvertently landing on Helena, who suffers injuries. During a visit to her hospital room, he offers to make amends, and she expresses a desire to join him for dinner.
As New Year’s Eve approaches, Boris hosts a celebration where each character finds themselves in new romantic entanglements: Marietta with Leo and Morgenstern, John with Howard, Melody with Randy, and Boris accompanied by Helena. The transformation of Melody and her parents is complete; they’ve embraced the liberal values of New York City, shedding their conservative Southern roots. Midnight strikes, and they all share kisses with their respective partners.
In a delightful twist, it becomes clear that only Boris can address the audience directly, imparting his final wisdom: to seek out all the joy life has to offer, succinctly stating, “Whatever Works.”
