At the beginning of Act 3, Proteus' servant Launce brings a letter to Julia from her lover Proteus, who has decided to stay in Italy. Julia learns he is no longer interested in her and is in love with another woman, Silvia. This news devastates Julia, and she vows to disguise herself as a boy named Sebastian to be near him.
As Julia travels to Milan to find Proteus, the mood of the play becomes increasingly somber. Julia's disguise allows her to enter the male-dominated world, but it also isolates her from her friends and family. She meets Silvia and becomes her confidante, all while struggling with her unrequited love for Proteus.
The turning point of Act 3 comes when Proteus and Thurio, another suitor of Silvia, find Julia, disguised as Sebastian, sleeping in the forest. Proteus draws his sword to kill Julia, but Silvia intervenes and begs for mercy. Proteus spares Julia's life but forces her to flee.
Julia's escape adds to the sense of despair in Act 3. She is now alone and friendless, and her hopes of winning back Proteus seem distant. The play ends with Julia's departure, leaving the audience with a sense of uncertainty about her fate.