Egeon, a merchant from Syracuse, is apprehended in Ephesus and condemned to death for violating a law that bars commerce and travel between the two cities. The only way he can avoid the penalty is to ransom his life for one hundred marks, a sum he neither has nor has any way of raising. Solinus, duke of Ephesus, asks the old man why he was traveling in the hostile city, and Egeon responds with his sad tale:
Over a quarter of a century earlier, Egeon and his wife, Emilia, became the parents of twin sons, and they soon followed that by buying another pair of twin boys, born “that same hour,” to be slaves for their own sons. They named both sons Antipholus and both slaves Dromio. In a shipwreck several years later, the family was separated. Egeon, with one twin son and his slave, was rescued by one ship; and his wife and the other two twins were rescued by another. Eighteen years later, the Antipholus raised by Egeon left Syracuse, along with his slave Dromio, to search the world over for his lost twin brother. When Antipholus and Dromio did not return after five years, his aged father set out on his own search, wandering vainly, only to be arrested and condemned to death in Ephesus on his way home.
Duke Solinus is moved by the sad tale and grants Egeon a reprieve until sunset to borrow the money required for his freedom.
Meanwhile, unknown to any of the other characters, the Antipholus raised by Egeon (now known as Antipholus of Syracuse) arrives in Ephesus with his slave, Dromio of Syracuse. Also unknown to anybody (but the audience) is the fact that the other Antipholus (now known as Antipholus of Ephesus) is already living in the city with his wife, Adriana, and the other slave, Dromio of Ephesus.
The stage is set and the series of “comedic errors” begins immediately and mounts throughout the play: Antipholus of Syracuse meets Dromio of Ephesus on the street and abuses him soundly because the slave tries to get Antipholus (the wrong master) to go “home” with him for dinner. Adriana locks her real husband out of their home because she is already in the house with his confused twin, Antipholus of Syracuse, whom she assumes is her husband. Antipholus of Ephesus refuses to pay Angelo the goldsmith for a gold chain he ordered, thinking he did not receive it (the chain was delivered to his surprised twin). Angelo wants his money and has Antipholus of Ephesus arrested. It is now Dromio of Syracuse (who is accused as being responsible for this) who is beaten by Antipholus of Ephesus (again, the wrong master).
As the situation grows more and more bewildering, with everyone certain that everyone else is totally mad, the duke is preparing for Egeon’s impending execution. Antipholus of Ephesus goes to the duke and, thinking himself terribly wronged, demands that he intercede for him. Egeon sees his son and thinks he is saved; but, of course, Antipholus of Ephesus is the other twin and hasn’t seen his father since he was a child and does not recognize him.
Finally, Antipholus and Dromio of Syracuse take refuge in an abbey, only to emerge to face the other two twins, as well as Egeon, who, all at once, has found not just one son, but two. Then, to complete the reunion, the abbess reveals that she too has been living under disguise and is actually Egeon’s wife, Emilia. Egeon’s life is ransomed, the family embraces, as do the Dromio twins, and all ends in happiness, with Emilia inviting all to discuss this “one day’s error” and “make full satisfaction.”