The play opens in a Nigerian marketplace in 1943 during World War II. Elesin Oba (the king's horseman) must complete an important cultural ritual. According to tradition, Elesin must follow his king to the afterlife by committing suicide. This ritual is important to the community as, according to Yoruba beliefs, it prevents their community from disappearing into an abyss or void.
The praise-singer is doubtful about Elesin’s intentions as he loves life so much. The women dance with Elesin and chant to celebrate his impending death. Elesin asks to wed a young woman. Iyaloja (the girl’s future mother-in-law) attempts to convince Elesin against this but eventually gives in so as to not disturb the order of the world.
Meanwhile, in a large house, Simon Pilkings, the British district officer, and his wife, Jane, prepare for a costume party and are dressed in egungun costumes (usually worn in honour of tribal ancestors). The police sergeant Amusa arrives to tell Simon Pilkings about Elesin’s plans to "commit death". He leaves, shocked at the Pilkings’ disrespect for African customs.
Simon tells his servant to ask Amusa to arrest Elesin. In the marketplace, Amusa and his constables try to get through a group of women who halt his progress and insult them for working for the English. Later, Elesin steps out of the stall the women were protecting and explains that his bride will now bear a child. He dances to the drums and under the praise-singer’s guidance, sinks into a trance-like state and prepares for death.
Olunde, Elesin's son, arrives at the Pilkings’ party. Their discussion becomes heated, especially when Olunde says that news of the king’s death brought him home to honour his father’s death. Elesin enters stage, handcuffed, and Olunde expresses his anger at his father’s inability to carry out his duty.
Locked in a cell, Elesin explains to Simon that disorder will result from his interference. A furious Iyaloja visits Elesin and criticises his dishonourable behaviour. A group of women enter with a large object covered with cloth and reveal Olunde's body. In response, Elesin pulls his chains tightly around his neck and strangles himself. Simon tries to resuscitate him, but Iyaloja tells him he must accept the consequences for disrespecting the Yoruba customs.
Elesin’s bride closes his eyes and pours dirt over them, and Iyaloja leads her off stage, talking of her unborn child.