Egeon, a merchant of Syracuse, is condemned to death in Ephesus for violating the ban against travel between the two rival cities. As he is led to his execution, he tells the Ephesian Duke, Solinus, that he has come to Syracuse in search of his wife and one of his twin sons, who were separated from him 25 years ago in a shipwreck.
The other twin, who grew up with Egeon, is also traveling the world in search of the missing half of their family. (The twins, we learn, are identical, and each has an identical twin slave named Dromio.) The Duke is so moved by this story that he grants Egeon a day to raise the thousand-mark ransom that would be necessary to save his life.
Meanwhile, unknown to Egeon, his son Antipholus of Syracuse (and Antipholus' slave Dromio) is also visiting Ephesus--where Antipholus' missing twin, known as Antipholus of Ephesus, is a prosperous citizen of the city. Adriana, Antipholus of Ephesus' wife, mistakes Antipholus of Syracuse for her husband and drags him home for dinner, leaving Dromio of Syracuse to stand guard at the door and admit no one. Shortly thereafter, Antipholus of Ephesus (with his slave Dromio of Ephesus) returns home and is refused entry to his own house. Meanwhile, Antipholus of Syracuse has fallen in love with Luciana, Adriana's sister, who is appalled at the behavior of the man she thinks is her brother-in-law.
The confusion increases when a gold chain ordered by the Ephesian Antipholus is given to Antipholus of Syracuse. Antipholus of Ephesus refuses to pay for the chain (unsurprisingly, since he never received it) and is arrested for debt. His wife, seeing his strange behavior, decides he has gone mad and orders him bound and held in a cellar room. Meanwhile, Antipholus of Syracuse and his slave decide to flee the city, which they believe to be enchanted, as soon as possible--only to be menaced by Adriana and the debt officer. They seek refuge in a nearby abbey.
Adriana now begs the Duke to intervene and remove her "husband" from the abbey into her custody. Her real husband, meanwhile, has broken loose and now comes to the Duke and levels charges against his wife. The situation is finally resolved by the Abbess, Emilia, who brings out the set of twins and reveals herself to be Egeon's long-lost wife. Antipholus of Ephesus reconciles with Adriana; Egeon is pardoned by the Duke and reunited with his spouse; Antipholus of Syracuse resumes his romantic pursuit of Luciana, and all ends happily with the two Dromios embracing.