A traveling merchant named Egeon from Syracuse breaks the law by entering Ephesus, where his people are banned due to a long-standing and bitter feud between the two cities. As he awaits his execution, he recounts to the Ephesian Duke how he came to be in Ephesus. He is searching for his son and his son’s servant, who are themselves on a quest for their lost twin brothers and Egeon’s wife, separated at birth by a shipwreck. Moved by Egeon’s tale, the Duke grants him one day to seek out someone who will pay his fine of one thousand gold marks and thus avert his execution.
That very day, Egeon’s son Antipholus of Syracuse (henceforth Antipholus S.) and his servant, Dromio of Syracuse (Dromio S.), arrive in Ephesus. Antipholus sends Dromio ahead to the inn with their belongings and money, totaling one thousand gold marks. The two are unaware that the brothers they seek live in Ephesus. Antipholus S. is approached by Dromio of Ephesus (Dromio E.), who mistakes him for his master, Antipholus of Ephesus (Antipholus E.) – and yes, both pairs of twins share the same name. Dromio E. has been sent by his master’s wife, Adriana, to bring him home to dinner. Confused, Antipholus S. scuffles with Dromio E. and that Dromio flees. He returns home and tells Adriana of his encounter with Antipholus S. Fearing this erratic behavior is caused by infidelity, Adriana sends Dromio E. out again to retrieve her husband.
Antipholus S. later encounters his Dromio and demands an explanation for his earlier behavior. Dromio S. is utterly confused and tells his master he has no memory of this previous encounter. The pair encounter Adriana and her sister Luciana, who mistake them for their Antipholus and Dromio. Adriana confronts a bewildered Antipholus S., and drags him home for dinner, leaving Dromio S. to guard the door.
Antipholus E. returns home with friends, and demands to be let into the house, but Dromio S. denies him access. Furious, he leaves to dine with a Courtesan, and requests that Angelo, a goldsmith, craft a chain that he may give to her. Antipholus S. is immediately taken with Luciana. Denying that he is her sister’s husband, he confesses his love for her. Luciana runs to her sister. Dromio S. shares that a kitchen servant is claiming him as her fiancée. Horrified, Antipholus S. and Dromio S. makes plans to leave Ephesus. Angelo returns with the gold chain promised for Antipholus E., and gives it to Antipholus S. He later demands payment from Antipholus E., who denies having received the chain and is arrested for refusing to pay.
Seeing Antipholus E. arrested, Dromio S. is sent home to Adriana and gets money in order to pay bail. He later gives this money to Antipholus S. Believing them to be their Ephesian counterparts, the Courtesan appears and demands Antipholus return the ring he borrowed during their dinner. Having never had the dinner, Antipholus refuses. Dromio E. encounters his actual master arrested and, having not brought money for bail, is verbally assaulted.
Adriana, Luciana, and the Courtesan bring a witch doctor named Pinch to exorcise Antipholus E.’s supposed madness. Antipholus E. and Dromio E. are tied up and sent off with Pinch. But then Antipholus S. and Dromio S. charge in, frightening the group who believe their Ephesian counterparts have escaped Pinch’s clutches.
The Syracusans later seek refuge in a nearby abbey. Egeon, unable to find the money needed to pay his fine, again awaits his execution. The execution is stalled by the appearance of Adriana and Antipholus E., who both give absurdly different accounts of their days to the Duke and demand justice against one another. Egeon greets Antipholus E. as his son, who claims he has never seen his father. The Duke summons the Abbess to clear the confusion, who brings the Syracusan Antipholus and Dromio, and her appearance remarkably helps to bring clarity to the events of the day.