Jazz is the story of a love affair between Joe Trace, a fifty-year-old married waiter and part-time cosmetics salesman, and Dorcas, a seventeen-year-old girl. When Dorcas leaves Joe for a younger man, he tracks her down at a party and shoots her. Dorcas refuses to implicate Joe, declining medical assistance and telling everyone who asks about the shooter, "I'll tell you tomorrow."

Tomorrow, of course, she is dead. Joe's wife Violet, reputed to be a crazy woman, goes to the funeral with a knife and attempts to disfigure the face of the beautiful girl in her casket. Violet is strong, but finally the ushers wrestle her to the floor. She has only managed to nick Dorcas under the ear.

Crazy Violet has a brief affair with another man. When that fails to move Joe, she decides to fall in love with him all over, but she is unable to bring herself to do more than fix his meals and iron his handkerchiefs. Instead, she decides to fall in love with, or at least learn more about, Dorcas. She begins to write notes to Dorcas's aunt, Alice Manfred, and then visits her. The two women develop a strange, uneasy friendship. Alice Manfred even lends Violet an unsmiling photograph of Dorcas, which she takes home and puts on the couple's mantle. During long sleepless nights, Violet and Joe take turns going in the parlor and staring at the dead girl's photo.

In the aftermath of the shooting, Violet and Joe each confront their motherless past, their childless present, and develop a friendship with Dorcas's best friend, Felice. Many events over three generations contribute to the reader's understanding of the tragic story.

The novel is based on a photograph taken at the funeral of a beautiful young girl in Harlem who refused to implicate her murderous lover. Morrison provides a synopsis of the plot in the novel's first five sentences. She proceeds to riff on the basic story like a jazz quintet, adding layers of meaning and transforming the tale into one of transcendent love set against the somber backdrop of violence in Harlem and the vibrant sounds of prohibition-era jazz music.