The Trials of Brother Jero follows a day in the life of Jero, a self-named prophet who is eager to present this turn of events to an audience to proudly illustrate his wise and cunning nature. The play opens with Brother Jero offering a monologue on his beginnings: He tells the audience that he was born a prophet and reveals his view of prophethood as a "trade." Jero was able to acquire his current beach-side realty in the name of his former master, the Old Prophet, by leading a campaign against the other prophets and followings also claiming the land. He then drove the Old Prophet off his own land, however, and midway into his monologue the Old Prophet enters to curse Jero, wishing his downfall via women. Jero presents this day as one in which the Old Prophet's wish is almost fulfilled.
In Scene 2 the audience is introduced to Chume, a messenger in the government, and Amope, his ill-tempered wife. Amope is determined to receive money that Brother Jero owes her for a velvet cape that he purchased from her, unbeknownst to Chume, who is his most faithful penitent. Amope camps outside his door and after a brief confrontation Jero sneaks out to the beach, where he tells his followers he lives. Chume arrives at the beach and meets Jero in Scene 3, eager to list his grievances about his wife. Jero has told Chume that he must not beat his wife, despite repeated requests from Chume. As the rest of the congregation gathers, a fight between a Drummer Boy and a woman temporarily distracts Jero, who leaves to attempt to mitigate the fight while Chume temporarily takes over his sermon, empowered. When Jero returns, exhausted, he discovers that Chume's wife is in fact Amope and grants him permission to beat her, hoping it will take care of his problems as well.
In Scene 4, Chume is emboldened to talk back to Amope. He soon discovers, however, that she man who is her debtor is in fact Brother Jero, and that his prophethood is built on a web of lies. Instead of beating Amope, he takes off to confront Jero. In Scene 5 Jero is in the process of converting another penitent, a Member of the House, by playing on his desire to become a Minister, when Chume arrives with the intention of killing Jero. Jero flees, as the Penitent interprets his disappearance as a sign of his divinity. When Jero returns he has arranged for Chume to be taken to an insane asylum, and his newest Penitent is more strongly convinced of his status as a Prophet, dedicating himself to Jero as his "Master."