It is a sultry Saturday night in Catfish Row, a dilapidated gated mansion converted into low-rent housing for Charleston’s black community. As the men return home from work, they assemble for a crap game, accompanied by the sound of a ragtime piano (Jazbo Brown’s Blues). Meanwhile, young mother Clara tries to sing her baby to sleep (Summertime). The crap game (Roll Dem Bones) is run by Sportin’ Life, a hipster and cocaine dealer, who has returned home after living in New York. Clara’s husband, Jake, accuses Sportin’ Life of using fixed dice in the game. Robbins enters, and despite protests from his religious wife, Serena, joins the crap game. He complains about his work in the cotton fields, and Jake offers him a job on his fishing boat. Robbins agrees, and throws his cotton hook to the floor. Jake and Clara’s baby is still not asleep, so Jake sings his own lullabye (A Woman Is A Sometime Thing). Porgy, a beggar and self-described cripple, enters, full of money collected from the white men downtown. The rough stevedore Crown is expected to join the game, but before he arrives, the men suggest that Porgy is soft on Crown’s woman, Bess. Porgy vehemently denies this, saying that as a cripple, he is destined to be alone (They Pass By Singin’). Crown and Bess arrive, and Sportin’ Life provides both with whiskey and cocaine, although both are already high and drunk. Crown bullies the rest of the men and eventually a fight breaks out. Crown murders Robbins with the latter’s discarded cotton hook. Bess insists that Crown leave the area before the police arrive. When he leaves, Bess tries to find shelter from the residents of Catfish Row, but her pleas are ignored by all of the residents except Porgy.
The next day, Serena holds a wake for her slain husband. All of her neighbors are there, singing a slow funeral chant (Gone, Gone, Gone). Porgy and Bess arrive together, and when Bess tries to make a donation to Robbins’ burial fund, Serena refuses her until Bess explains that Porgy is now providing her money. Serena and Porgy inspire the congregation to donate more money to the fund (Overflow). The police arrive, but are unable to determine who killed Robbins. They arrest Peter, the honey man, as a material witness. Serena sings a wailing lament for her lost love (My Man’s Gone Now). The detective informs Serena that Robbins must be buried by the next day or his body will be given to the medical students. While the fund is still short, the undertaker agrees to bury the body anyway. The scene concludes with an enthusiastic spiritual (Leavin’ For the Promised Land).
A month later, Jake and his fishermen are preparing for a trip to the Blackfish Banks, despite Clara’s warning that the September storms are due (It Takes A Long Pull To Get There). Jake argues that working is the only way to earn money for their son’s college education. Porgy overhears the conversation and sings that his life is much less stressful (I Got Plenty o’ Nuttin’). The neighbors note that Porgy is more agreeable since Bess started living with him. Clara reminds Jake that a community picnic on Kittiwah Island is happening later in the day, and Jake agrees to postpone the fishing trip until the next day. Sportin’ Life turns up, but is treated with hostility by Maria, one of the elder women in the community (I Hates Yo’ Struttin’ Style). A sleazy lawyer named Frazier tries to sell Porgy a divorce between Crown and Bess, even though those two were never wed. A white man named Archdale enters and explains to Porgy that because his family used to own Peter’s family, he will pay for Peter to be released from jail. Archdale also sees Frazier and warns him to stop selling phony divorces. A great buzzard flies overhead, sparking Porgy’s deep superstitions (Buzzard Song). Sportin’ Life tries to tempt Bess with more cocaine, but she refuses, saying that she is now off drugs and living well with Porgy. The title pair declares their love for one another (Bess, You Is My Woman Now). The parade to the picnic begins (Oh, I Can’t Sit Down), but Bess hesitates about attending the picnic and leaving Porgy home alone. Encouraged by Maria and Porgy, Bess decides to join the group.
The picnic is supposedly a church function, but it turns into wild revelry (I Ain’t Got No Shame) with Sportin’ Life offering his own interpretation of several famous Bible stories (It Ain’t Necessarily So). Serena rebukes them all as the boat arrives to take the group home. Bess is about to leave when Crown reappears. He has been living on the island since the murder, but says he is coming back to get Bess in a few weeks. Bess tries to explain that she is now living with Porgy, but Crown laughs off the idea and grabs Bess to keep her from catching the boat. She tries to convince Crown that she’s not worthy of him (What You Want Wid Bess?), but Crown forces himself on her and the boat leaves for the mainland without her. When Bess finally returns several days later, she is delirious with fever. Serena prays over her (Oh, Doctor Jesus) and claims that Bess will be well again by the end of the day. As Porgy waits, several local sellers (including Peter) sing of their wares (Here Come de Honey Man, Strawberry Woman, Devil Crab). As predicted, Bess is well by evening, and she explains her dilemma with Crown to Porgy (I Wants To Stay Here, aka I Loves You, Porgy). Porgy is determined to continue living with Bess, and to deal with Crown whenever he returns.
Clara stands on the wharf, awaiting Jake’s return. Although the weather is still calm, she worries that the water is black and menacing. A hurricane bell sounds and everyone from Catfish Row huddles in Serena’s room, Several prayers are sung simultaneously (Oh, Heavenly Father) before the group unites in a spiritual (Oh, The Lawd Shake De Heavens). As the hurricane rages, there is a fierce knocking at Serena’s door (Oh, There’s Somebody Knockin’ at de Do’). It is Crown, who has fought the storm and claims that he and God have wrestled with each other (If Gawd Want To Kill Me). Serena tries to engage the group in another spiritual, but Crown orders them to stop and provides his own profane reply (A Red-Headed Woman). Clara looks out the window and sees Jake’s fishing boat upside down in the water. She hands her baby to Bess and runs out into the storm. All of the other men are afraid to go out after her, so Crown goes back outside, saying that he and the Lord will fight another round, Clara, Jake and Crown are all feared lost in the storm (Clara, Clara). Sportin’ Life laughs off the mourning rituals and suggests that Crown is still alive. Bess tries to ignore him and sings to the baby now in her care (Summertime). When the courtyard empties, Crown re-appears. He sneaks to a place under Porgy’s open window, but before he can crawl into Porgy’s room, Porgy extends his hand out the window and stabs Crown to death.
The police don’t believe that Porgy has committed Crown’s murder, but take him to the morgue to identify the body. Sportin’ Life tells Porgy that Crown’s wounds will bleed again when the murderer views them, and Porgy decides not to look at the body. He is detained under contempt of court. Sportin’ Life takes advantage of the situation by getting Bess hooked on cocaine again and convincing her to go to New York with him (There’s A Boat Dat’s Leaving Soon For New York). Eventually, the police release Porgy. He returns to Catfish Row with high spirits and several presents (bought with money won in prison crap games). He is crushed when he finds out that Bess has left with Sportin’ Life (Oh, Bess, Where’s My Bess?) and vows to leave Catfish Row to find her and bring her back home (Oh, Lawd, I’m On My Way).