Summary
Antipholus S. enters, having been to the Centaur inn, and reports that Dromio has stored his gold safely there. Dromio S. enters. Antipholus S. teases Dromio about the conversation he had with Dromio E. about the gold and the dinner, which naturally Dromio S. does not remember. Dromio S. believes he is joking, and gets another beating from his angry master. Dromio S. manages to soothe his master into a better humor with a long joke about baldness.

Adriana and Luciana enter. Adriana is annoyed and upset at Antipholus S.'s failure to recognize her. She accuses him of infidelity and of having betrayed his marriage vows. Antipholus S. protests that he has never seen her before, and Dromio S, confirms that he also does not know her, which makes her even angrier. Though Antipholus S. is still baffled, he decides to go along with "the offer'd fallacy" (line 186) and go with Adriana to her home. Dromio wonders if he has been transformed into an ape or a donkey, as this would explain why Adriana knows him but he does not know her.

Antipholus S. arrives at Antipholus E.'s house with Adriana and goes upstairs with her and Luciana to dine. Dromio is left to guard the gate, with instructions from Adriana to let no one in.

Analysis
Adriana's enraged speech to Antipholus S., whom she believes to be her adulterous husband (she is mistaken on both counts) takes up the image of the drop of water introduced by Antipholus S. in Act 1, scene 2. She says that husband and wife are as indivisible, just as a drop of water placed into the ocean cannot be retrieved. Her idea of love is not only possessive in the extreme but demands the complete obliteration of all individual identity - a notion that proves as unsustainable in the play as it does in real life. She takes this idea to its logical conclusion, saying that "if we two be one, and thou play false, / I do digest the poison of thy flesh, / Being strumpeted by thy contagion" (lines 142-144). In other words, she feels she is as responsible as he is for any sin that he commits.

The characters' confusion of identity is highlighted by Dromio S.'s jesting query as to whether he has been changed into an ape or an ass. Since both animals carried connotations of foolishness, he is in fact asking if he, and by extension his master, are being made fools of. Antipholus S.'s bewildered question, "Am I in earth, in heaven, or in hell? / Sleeping or waking, mad or well advis'd?" (lines 212-213) sums up the absence of constant reference points and solid assumptions in this shifting world.

Antipholus S.'s essential good humor is apparent in this scene. Dromio S. is able to laugh him out of his determination to beat him, and Antipholus cheerfully decides to go along with Adriana's "offer'd fallacy" even though he has never seen her before. This shows that he is open to new experiences, an important quality in a comic hero.