The Piano Lesson takes place in the Pittsburgh home of Doaker Charles, his niece Berniece, and her young daughter Maretha. It’s 1936. The Charleses are an African American family originally from rural Mississippi; they have brought with them a beautiful upright piano decorated with carvings resembling African masks.
At five o’clock one morning, Berniece’s brother Boy Willie and his friend Lymon show up at the house. They’ve driven from Mississippi with a truckload of watermelons they hope to sell. Boy Willie reports that Sutter, the current owner of the farm on which the Charles family was once enslaved, has just died. It’s rumored that the “Ghosts of the Yellow Dog” pushed Sutter down a well. Berniece dismisses this story as nonsense and mistrusts the young men’s business in Pittsburgh. She tells them to sell their watermelons quickly and then goes back to bed.
Lymon tells Doaker that he’s hoping to settle down in Pittsburgh and start a new life. Boy Willie, on the other hand, wants to sell the family piano to help him save up enough money to purchase the late Sutter’s land. Doaker warns Boy Willie that Berniece won’t agree to this plan. Just then, they hear Berniece shouting from upstairs. She runs into the room, claiming that she saw the ghost of Sutter upstairs, and she accuses Boy Willie of having killed Sutter. Boy Willie denies it and says that Sutter is probably haunting her because of the piano—a sign that she should get rid of it. Soon after, Berniece’s boyfriend, Avery Brown, drops by and tells Boy Willie and Lymon about his plans to become a preacher and start a church.
A few days later, Doaker’s brother Wining Boy (a failed musician) drops by for a visit. Boy Willie and Lymon, who still haven’t sold their watermelons, reminisce with Wining Boy about serving time on Mississippi’s Parchman Farm. After their release, the men were pursued by the local sheriff for having stolen some wood. Berniece’s husband, Crawley, was shot and killed in the confrontation. Later, Lymon was imprisoned for not working, and after the judge required him to work for a local white man named Stovall in order to pay off his bail, Lymon began hiding out in his truck instead.
During the same conversation, Doaker tells Lymon the history of the family piano. Back when the Sutter family enslaved the Charles family, the Sutter ancestor traded two of the Charles family members—Boy Willie’s and Berniece’s great-grandmother Mama Bernice and grandfather Papa Boy Charles—for the piano, as a gift for his wife, Ophelia Sutter. But Ophelia missed her slaves, so the Charles’s great-grandfather Papa Boy Willie was made to carve his wife’s and son’s images on the piano for Ophelia to remember them by. He also carved images of other family members and family events.
A couple of generations later, Boy Willie’s and Berniece’s father, Boy Charles, was obsessed with the Sutter piano and the fact that, by owning it, the Sutters still owned a piece of the Charles family. So his brothers, Wining Boy and Doaker, helped him steal the piano. Though they succeeded, Boy Charles was caught and burned to death in a boxcar as a result. This is why Berniece refuses to sell the piano to this day. Boy Willie insists that if his father knew that Boy Willie had the chance to become a landowner, he would have been happy for Boy Willie to sell the piano. He and Berniece fight over this, with Berniece blaming him for Crawley’s death as well. They’re interrupted by the screams of young Maretha, who thinks that she saw Sutter’s ghost upstairs.
That night, Berniece is about to take a bath when Avery drops by. His plans to start a church are moving forward, and he wants Berniece to marry him. Berniece insists she isn’t ready, and she resents Avery’s insistence that she needs someone to take care of her. Avery tells her that she can’t carry Crawley’s memory—or the sorrowful memories associated with the piano—around with her forever. Though Berniece continues to refuse him, Avery agrees to come over tomorrow to attempt to bless the house and to hopefully dispel Sutter’s ghost.
That same night, Boy Willie and Lymon, finally successfully in selling their watermelons, go out on the town to spend some money and meet women. A drunk Boy Willie comes back with a woman named Grace, but Berniece hears their racket and kicks them out. Shortly thereafter, Lymon comes home, and he and Berniece chat about Lymon’s job prospects and his hopes to find a nice woman to share his new life with. He and Berniece end up kissing before parting ways for the night.
The next day, Boy Willie wakes up Lymon with the news that he’s going to sell the piano to a white man who collects musical instruments. He and Lymon struggle to heft the heavy piano toward the truck without success, and Doaker, who’s largely stayed out of Boy Willie’s argument with Berniece, firmly warns them to stop what they’re doing.
Later, Berniece and Boy Willie have another confrontation over Boy Willie’s determination to sell the piano. Boy Willie tells Berniece that she’s sending Maretha into the world at a disadvantage by not telling her about the piano’s history and thereby giving her something to take pride in. He tries to persuade Berniece that by selling the piano, all he’s trying to do is leave his mark on the world, like their father did.
Soon after this, Avery arrives to bless the house, just as Lymon arrives with rope to help load the piano. Berniece, holding Crawley’s gun, warns Boy Willie that he isn’t taking the piano anywhere. When everyone perceives the presence of Sutter’s ghost, Berniece urges Avery to begin the house blessing. As Avery begins praying and reading from the Bible, however, Boy Willie—who’s been mockingly calling out to Sutter’s ghost—finds himself being choked and thrown about by the unseen spirit. Avery is helpless, and from an unexplainable impulse, Berniece suddenly realizes what she has to do. She sits down and begins playing the piano for the first time in many years, calling upon her parents and other ancestors to help her. As calm finally descends on the house, Berniece chants words of thanks to her ancestors. Boy Willie decides to catch a last-minute train home to Mississippi instead of selling the piano, and in farewell, he tells Berniece that if she and Maretha don’t keep playing it, both he and Sutter’s ghost might be back.