Feste proves Olivia the fool for mourning; Malvolio dismisses the fool; Cesario arrives and delivers Orsino's message. Olivia falls in love and sends a ring.
Feste returns to Olivia's house after an unexplained absence. Maria warns him he will be in trouble with their mistress. When Olivia enters with Malvolio, she orders Feste away. Feste refuses and begins to argue: Olivia is the fool, not him, because she mourns her dead brother when he is in heaven and happy. She is weeping in the wrong place. Olivia is amused. Malvolio, asked his opinion, says Feste is past his prime and should not be indulged. Olivia gently rebukes Malvolio for his self-love and defends Feste.
Malvolio brings word that a young man from Orsino refuses to leave until he has spoken with Olivia. Sir Toby, briefly visible and drunk, is sent to deal with him. He is useless. Olivia eventually relents and agrees to receive the visitor.
Cesario enters and delivers Orsino's message with confidence: Orsino is consumed by love. Olivia is not impressed; she has heard this before. She refuses Orsino, firmly but politely. When Cesario asks what she should tell the Duke, Olivia says she cannot love him, and nothing will change that.
Cesario then asks what Olivia would do if someone loved her the way she loves herself. The speech builds in passion, describing the willow cabin she would build at Olivia's gate if she were Orsino. Olivia begins to pay close attention.
After Cesario leaves, Olivia marvels at what just happened: how quickly she has fallen. She sends Malvolio after Cesario with a ring, claiming the young man left it, which is not true. The ring is Olivia's first act of romantic pursuit.
This scene is the most dramatically dense of Act 1, balancing three distinct tones: the wit of Feste's exchange with Olivia, the pompous dismissal of Malvolio, and the sudden emotional stakes of Olivia's response to Cesario.
Feste's proof that Olivia is a fool is more than a joke. He makes a genuine argument: if she believes her brother's soul is in heaven, she is crying for someone who is happy. The logic is sound, and Olivia laughs instead of defending herself. This is the first crack in the posture of seven years' grief. Her willingness to be shown wrong by her own fool, and her defence of him against Malvolio, reveals that Olivia is intelligent, self-aware, and considerably more flexible than her vow of mourning implies.
Malvolio's dismissal of Feste is the scene's first clear view of his character. He does not enjoy wit that does not serve him. He cannot accept that a social inferior might have the better of an argument. His recommendation that Olivia ignore Feste is also, subtly, a power play: he is positioning himself as the sensible authority against the licensed fool. Olivia's response, telling him he is sick of self-love, is the most accurate diagnosis in the scene.
Cesario's willow cabin speech is the scene's turning point. "Make me a willow cabin at your gate, / And call upon my soul within the house; / Write loyal cantons of contemned love / And sing them loud even in the dead of night." The passion is real: Viola is describing exactly the kind of love she herself feels for Orsino, spoken in Orsino's name. The irony is that this speech, which Viola cannot mean for herself, is the thing that makes Olivia fall in love.
The ring is the scene's most technically precise moment. Olivia tells Malvolio to return it as something Cesario left behind. Cesario left no ring. The fiction is polite, but it is still a fiction: Olivia is initiating a pursuit she cannot openly acknowledge.