The story opens with the town of Guellen (which literally means "excrement") preparing for the arrival of famed millionairess Claire Zachanassian. The town is in a state of disrepair, and the residents are suffering considerable hardship and poverty. They hope that Claire, a native of the small town, will provide them with much-needed funds. Alfred Ill, the owner of Guellen's general store and the most popular man in town, was Claire's lover when they were young, and agrees with the Mayor that the task of convincing her to make a donation should fall to him. As the town gathers at the railway station to prepare for Claire's arrival, they are met with an unexpected surprise when Claire steps off of an earlier train. She is grand, grotesque, and fantastic, and is accompanied by two henchmen, her husband, a butler, and two eunuchs, along with a coffin, a caged black panther, and various pieces of luggage. She begins a flirtatious exchange with Ill, and they promptly revisit their old haunts: Petersen's Barn and Konrad's Village Wood. Ill finds her as delightful as ever, though they are both now in their sixties and significantly overweight. Claire draws Ill's attention to her prosthetic leg and artificial hand.
After settling into the Golden Apostle Hotel, Claire joins the rest of the town, who have gathered outside for a homecoming celebration. A band plays, gymnasts perform, and the Mayor gives a speech. Claire takes the opportunity to announce that she will make a donation of one million dollars, half for the town and half to be shared among the families. The townspeople are overjoyed, but their happiness is dampened when Claire's Butler steps forward to reveal her condition. The Butler was once the Lord Chief Justice of Guellen, and had overseen the paternity suit that Claire had brought against Ill in 1910. In the suit, Ill had produced two false witnesses (who have since been transformed into Claire's eunuchs), and the court had ruled in his favor. Ill went on to marry Matilda, who owned the general store, and Claire moved to Hamburg and became a prostitute. She declares to the townspeople that she has come to Guellen to prove that justice can, indeed, be bought. Her donation is conditional on Ill's death. When the Mayor refuses, the town cheers in support, but Claire states rather ominously, "I'll wait."
Ill feels generally confident about his status in the town. However, as time passes, he begins to feel troubled about their growing discontent, and then increasingly fearful as he begins to notice the proliferation of new yellow shoes on the feet of the townsmen, and the fact that everyone seems to be purchasing especially expensive items on credit. He goes to see the Policeman to demand that he arrest Claire for having threatened his life, but the Policeman tells him that the threat is nonsense. Ill then turns to the Mayor, who echoes similar sentiments. Both figures are armed, because Claire's black panther has escaped from his cage and is prowling about the town. This only feeds Ill's fear, since "my black panther" was Claire's pet name for him in their youth. He runs to see the Priest, but the Priest seems to be turning away from him as well, as he effectively ignores Ill's fears and instead draws attention to the magnificent new church bell. Slowly, the standard of living in the town rises, even though the townspeople continue to assure Ill that he is safe. Claire then receives the news that her black panther has been killed, and she has a funeral song played in its memory.
In an effort to escape, Ill heads to the railway station, but finds that, strangely, the entire town is gathered there. They ask him where he is going, and he says that he is planning to move to Australia. They wish him well, again assuring him that he has nothing to fear in Guellen, but Ill grows increasingly nervous nonetheless. The train arrives, but he decides not to board, believing that someone will stop him anyway. Paralyzed, he collapses in the crowd, crying, "I'm lost!"
After some time passes and Claire weds a new husband in the Guellen Cathedral, the Doctor and the Schoolmaster go to see her and explain that the townspeople have run up considerable debts since her arrival. The Schoolmaster appeals to her sense of humanity and begs her to abandon her desire for vengeance and help the town out of the goodness of her heart. She reveals to them that she already actually owns all of properties in the town, and that she is the reason the businesses have been shut down and caused stagnation and poverty for the citizens. The Doctor and the Schoolmaster are aghast at this revelation.
In the meantime, Ill has been pacing the room above the general store, his terror growing as the townspeople buy more and more expensive products on credit. News reporters, having received word of Claire's imminent wedding, are everywhere, and they enter the store to get the scoop on Ill, having heard that he was Claire's lover back in the day. The Schoolmaster, drunk, tries to inform the press about Claire's cruel proposal, but the townspeople stop him. Finally Ill descends the stairs, surprised at the hubbub, but quiet. The reporters clear the room when they hear that Claire has just divorced the man she has just married, and has found a new lover.
After the confusion has cleared, the Schoolmaster and Ill have an honest discussion. The Schoolmaster explains that he is certain that Ill will be killed, and admits that he will ultimately join the ranks of the murderers. Ill calmly states that he has accepted his guilt, and acknowledges that the town's suffering is his fault. The Schoolmaster leaves, and Ill is confronted by the Mayor, who asks whether Ill will accept the town's judgment at that evening's meeting. Ill says that he will. The Mayor then suggests that Ill make things easier on everyone and shoot himself, but Ill refuses, insisting that the town must go through the process of actually judging and then killing him.
Ill goes for a ride in his son's newly-purchased car, accompanied by his wife, Matilda, and his daughter, both of whom are wearing new outfits. As they drive through Konrad's Village Wood, Ill says that he is going to go for a walk through the woods before heading to the town meeting. His family continues on to the movie theater. In the woods, Ill comes across Claire, who is walking with her newest husband. She asks her husband to leave so that she and Ill can speak privately. They reminisce about the past, and make plans for the future. Claire tells Ill that she plans to take his body away in the coffin to a mausoleum in Capri that overlooks the Mediterranean. She also tells Ill that she has never stopped loving him, but that over time her love has grown into something monstrous.
The town meeting is flooded with press, and the town publicly announces their acceptance of Claire's donation. They then go through the formality of a vote, which is unanimous, and the Mayor states that they have Ill to thank for their new-found wealth. The press is then ushered out of the auditorium to enjoy refreshments. The doors are locked, and the lights are dimmed. The Priest crosses Ill, and he is killed by the townsmen. Just as a reporter reappears in the auditorium, the Doctor announces that Ill has died from a heart attack. The reporters gather, and declare that Ill has died from joy. Claire examines the corpse, gives the Mayor his check, and leaves the town with Ill's body in the coffin that she brought with her when she arrived in Guellen. Claire boards the train at the railway station, and the visit comes to an end.