It all begins when Boy Willie and Lymon arrive in Pittsburgh from Mississippi with a truckload of watermelons. The two bust into the house of Boy Willie's uncle, Doaker, at five in the morning. We soon learn Boy Willie's big plan. He's going to sell the watermelons and the family's historic piano, so that he can buy Sutter's land – this is the land on which his family was once enslaved. Sutter has recently died and Boy Willie is determined to make the land his. Berniece, Boy Willie's sister, is dead-set against selling the piano, however, because it is valuable family heirloom. The play becomes something of a ghost story when the ghost of Sutter appears to Berniece, calling Boy Willie's name.
As the act progresses, Doaker tells the story of the piano and we learn why Berniece is so attached to it. The family history was carved into the piano by Berniece and Boy Willie's great grandfather, while he was still in slavery, and their great grandmother and grandfather were traded for it. On top of all that, Berniece and Boy Willie's father even died over it, when he was set on fire in a boxcar after taking the piano from Sutter's house.
The conflict between Berniece and Boy Willie continues throughout the play. Berniece thinks that selling the piano would be the same as selling their souls. Boy Willie, on the other hand, feels that the best way to honor the memory of his ancestors is by putting the piano to use. Berniece no longer plays on the piano, because it brings to mind too many painful memories, and Boy Willie sees this as letting their family legacy go to waste.
As the conflict between the two siblings builds, the ghost of Sutter seems to gain more and more power. The play reaches its climax when Boy Willie and Lymon attempt to roll the piano out of the house. Berniece threatens Boy Willie with a gun, and the ghost of Sutter strikes again. Avery, a preacher, attempts to exorcise the ghost, but fails. Boy Willie wrestles it, but seems to be fighting a losing battle. At last, Berniece saves the day when she plays the piano, calls on the spirits of her ancestors, and banishes Sutter's ghost. In the end, Boy Willie heads back down to Mississippi without selling the piano. Before leaving, though, he reminds his sister to keep playing on the piano, or he and Sutter many just be back.