In 1958 Harlem, New York, Stix Warren, Levi Brown, and the three Williams sisters—Sister, Dolores, and fifteen-year-old Sparkle—sing in the church choir. Later, they sit on their tenement steps as Stix works on a song for them. After their mother, Effie Williams, calls them upstairs for the evening, Dolores, the middle sister, expresses her resentment that her mother rides a train several hours every day to work as a maid for white people on Long Island. The next day, when Sparkle takes the family’s wet laundry to hang on the roof, Stix waits for her. He kisses her, but Sparkle says such intimacy is a sin, even though she likes it. Meanwhile, Levi kisses more passionately with Sister, the oldest sister, in a borrowed car. Sister wants a man who can afford “the big time,” and Levi swears he can give it to her. Stix goes to Shimmy Dodson’s record store, where Stix works part time, and gets five promotional passes to the Moonlights’ show at the Brooklyn Paramount Theatre that Shimmy received from the Moonlights’ record label. After Stix, Levi, and the sisters attend the show, Stix is convinced they can form a doo-wop group like the Moonlights. The quintet, calling themselves the Hearts and featuring Sister on lead vocals, rehearses Stix’s songs, and he gets them a spot on a burlesque house’s amateur contest night. The group wins the approval of the crowd, along with prize money. However, when Stix and Levi ask a nightclub owner to book the Hearts, the man says he wants only the three sisters. Losing interest in the group, Levi attends a local cockfight, asks his friend Ham for an introduction to wheeler-dealer Satin Strothers, and convinces Strothers to hire him to run errands. Meanwhile, Stix and the Williams sisters use their contest prize money to buy musical arrangements for Stix’s songs and three red dresses for the new group, now called Sister & the Sisters. With choreography and new songs, the trio pleases the nightclub crowd and gets booked as regulars. Satin goes backstage, sees Sister, and tells his date to leave; when the woman objects, Satin takes her into a hallway, punches her, and tells Levi to get her out of the club. Stix takes Sparkle to a hotel and they make love for the first time. A few months later, Levi asks Satin for more responsibility in Satin’s organization, because he wants more money, but Satin says that Levi is not yet ready. When Effie Williams and her friend, Mrs. Waters, attend the nightclub without notice, Stix sits them at Satin’s table. Remembering the night Sister packed her bags and left the apartment, Effie realizes her daughter is living with Satin, a known criminal. Backstage, Dolores gets angry at Satin because Sister has a black eye, but Sister throws her out of the dressing room and snorts cocaine. When Effie goes backstage after the show, she warns Sister that Satin will drag her into the gutter. The next day, at a house on Long Island, Effie’s employer, Mrs. Gerber, sees she is in distress and offers her friendship. That night, Satin beats Sister, and when Dolores later sees her in the dressing room, she is shocked at Sister’s bruises. Sister says she sent Sparkle for makeup, but Sparkle returns with heroin. Determined to get back at Satin, Dolores seduces Ham, his right-hand man, and learns that Satin will make his next drug pickup under the Manhattan Bridge. After Dolores alerts police, two undercover officers break up the transaction, but instead of Satin, they capture Levi. Pulling Stix into an alley, Satin accuses Stix of calling police, but Stix pounds him into submission. Dolores packs her bags and tells her mother she is leaving Harlem to start a new life, without relying on the “white man” and “being his maid.” At the Gerbers’ house, Effie serves a dinner party of tough-looking gentlemen and hears them toast their new company, Americus Enterprises. Meanwhile, the group replaces Sister with a heavy-set neighborhood girl, Tune Ann, but the club owner tells Stix he no longer wants them to perform. Stix tells Sparkle he is going upstate to work in construction and wants her to go with him, but Sparkle is too concerned for her sister to leave Harlem. Before dying of a drug overdose, Sister sings a torch blues, “Giving Up,” at a jazz club, and Sparkle later sings “Take My Hand, Precious Lord” at Sister’s funeral. Stix returns to work for a record company, reunites with Sparkle, and starts her solo career, but Sparkle is uninspired to sing. At Effie's insistence, Sparkle visits Stix at the studio where he works, and they reconcile with a kiss. He rehearses with Sparkle and plans to make a record, but needs $10,000 to kick-start Sparkle’s career. When Sparkle says she knows only one man with that kind of money, Stix visits Effie’s employer, Moe Gerber, and Moe agrees to borrow the money from his business associates. Sparkle records two of Stix’s songs and he secures a record company contract. Her single climbs the Billboard charts. Stix returns the $10,000 to Moe Gerber, with sixteen percent interest, but Moe says his associates want “a piece” of Sparkle’s success instead of the money. Moe explains they are dealing with the Mafia. That night, Sparkle opens for Ray Charles at Carnegie Hall under the name Sparkle Williams and the Soul Ladies, but before the show begins, two gangsters grab Stix outside, throw him in the back seat of a Cadillac, and drive him to a warehouse. One mobster puts a gun to his head and plays Russian roulette, but Stix refuses their deal. They relent and return him to Carnegie Hall, where he joins Effie backstage. Sparkle sings her final number and walks offstage into Stix’s arms to wild applause.