Final answer:
Viola/Cesario learns that Malvolio has mistaken her for Sebastian, and she plans to solve the misunderstanding.
Step-by-step explanation:
Viola/Cesario learns from her/his encounter with Malvolio that Malvolio has found a love letter from Olivia, addressed to Viola's brother Sebastian. Viola realizes that Malvolio has mistaken her for Sebastian and believes that Olivia is in love with her. Viola plans to solve this misunderstanding by revealing her true identity to Malvolio and explaining the confusion. In the play 'Twelfth Night,' Viola/Cesario's encounter with Malvolio leads to a comedic mix-up and eventually resolves itself with the truth coming to light.