Antipholus of Ephesus -- whom we see for the first time -- arrives home, accompanied by Dromio of Ephesus, the goldsmith Angelo and the merchant Balthasar. Aware that he is late for dinner, he warns them, "My wife is shrewish when I keep not hours." Evidently Dromio has told him about being beaten by Antipholus-S. and accused of having stolen a thousand marks, but Dromio persists in his story. But remembering his guests, Antipholus assures them that all will be well and that they'll be welcome for dinner. Then he's startled to find the gate barred, and orders Dromio to see to it that it's opened.
Dromio E. then begins arguing with Dromio S., who is on the other side of the door. (This presents a little staging problem, especially after Dromio S. is joined by the servant Luce and later when Adriana appears inside the house.) Dromio-E. calls out for other servants to open the door: "Maud, Bridget, Marian, Cicely, Gillian, Ginn!" Evidently Antipholus-E. and Adriana have a large complement of female servants. Dromio-S. has been ordered by Adriana to guard the door well, so he refuses to open it. When Antipholus-E. asks who is barring the door, Dromio-S. answers, "The porter for this time, sir, and my name is Dromio." Dromio-E. is infuriated that someone has "stol'n both mine office and my name."
When Luce, Adriana's maid, shows up on the other side of the door, Dromio-E., hearing her voice, asks her to let Antipholus in, but she says "he comes too late." (She seems to be unaware that Adriana is already dining with the other Antipholus.) Then Adriana enters and Antipholus-E., hearing her voice, calls out, "Are you there, wife?" Adriana denies that she's his wife and orders him to get away from the door, then exits with Luce.
Angelo and Balthasar suggest that this isn't a good time for them to visit, but Antipholus-E. persists in trying to break the door in, asking Dromio-E. to "borrow me a crow," which occasions some confusion about why Antipholus wants a bird until he specifies "an iron crow." Balthasar tries to reason with Antipholus that he should take into account Adriana's reputation for virtue and assume that she has good reason for barring the door. People will talk, he suggests, if Antipholus makes a scene and breaks down the door. They should go dine elsewhere and come back later.
Antipholus yields to the argument and says, "I know a wench of excellent discourse / Pretty and witty; wild and yet, too, gentle; / There will we dine." Evidently Adriana's suggestions that Antipholus is unfaithful to her are not unfounded. He tells Angelo to get the chain he has been planning to give Adriana and bring it to him at the Porpentine, "For there's the house -- that chain will I bestow / (Be it for nothing but to spite my wife) / Upon mine hostess there." Angelo agrees to meet him there with the chain in about an hour.
Antipholus of Syracuse leaves the house with Luciana, who is pleading the case for her sister, telling him that even if he has fallen out of love with Adriana, he should not treat her harshly, but at least pretend to still be in love with her. "Apparel vice like virtue's harbinger; / Bear a false presence, though your heart be tainted." But Antipholus-S. has begun to fall for Luciana, and starts to woo her: "Less in your knowledge and your grace you show not / Than our earth's wonder, more than earth divine," which some think may be a flattering allusion to Queen Elizabeth, before whom the play may have been performed. He is also still somewhat persuaded that he is the victim of something supernatural:
Are you a god? would you create me new?
Transform me then, and to your power I'll yield.
But if that I am I, then well I know
Your weeping sister is no wife of mine,
Nor to her bed no homage do I owe;
Far more, far more to you do I decline.
It's Luciana's turn to think he's mad, and finally, after putting up with his wooing for somewhat longer than she really needs to, she goes off to fetch Adriana. Meanwhile, Dromio-S. runs in to say that he is being wooed by Nell, Adriana's "kitchen wench." (There is some discussion whether this is the same person, under a different name, as Luce, but since Nell never appears on stage, the confusion seems unnecessary. Given that we've already heard the names of six other female servants in the household, there's no reason that Dromio-E. wouldn't have been fooling around with several of them.) Nell, at any rate, Dromio-S. reports, is "all grease, and I know not what use to put her to but to make a lamp of her, and run from her by her own light." There follows some shtick between Antipholus and Dromio about Nell's globe-shaped body and where the various countries might be found on her person; Shakespeare's only direct reference to "America" is included in the tour de Nell. Evidently Dromio-E. and Nell have been fairly intimate, for she describes to Dromio-S. some of the moles and warts the two Dromios apparently share, and he, "amazed, ran from her as a witch." This accords with Antipholus-S.'s suspicions about what is going on in Ephesus:
There's none but witches do inhabit here,
And therefore 'tis high time that I were hence;
She that doth call me husband, even my soul
Doth for a wife abhor. But her fair sister,
Possess'd with such a gentle sovereign grace,
Of such enchanting presence and discourse,
Hath almost made me traitor to myself;
But lest myself be guilty of self-wrong,
I'll stop mine ears against the mermaid's song.
But then who should show up but Angelo, the goldsmith, with the chain he's delivering to the other Antipholus at the Porpentine. He gives it to Antipholus-S., who is, naturally, puzzled about it, but Angelo, thinking that Antipholus is joking, calls him "a merry man," and hurries off, saying he'll come back at supper time for the payment. Antipholus then goes out to see if there are any ships ready to set sail from Ephesus.