This scene is not only the longest scene in the entire play, it is also longer than the entirety of Act IV and the entirety of Act V. Likewise, there are many divisions within this scene in terms of several different groupings of characters on the stage and several uses of mistaken identities. Malvolio is mistaken for a madman by Olivia, Olivia is mistaken for a true love by Malvolio, Viola is mistaken for a man who allegedly insulted Sir Andrew, Viola is mistaken for a man with a "heart of stone" by Lady Olivia, and Viola is mistaken for her brother Sebastian by Antonio.
Before Malvolio arrives, Maria warns Olivia (and the audience) that Malvolio is "possessed," that he is out of his mind and that his sanity has been taken over (possessed) by devils. When Malvolio does appear, we are not disappointed. As in other scenes in Twelfth Night, the staging is an extremely important part of the total effect. As Maria goes out and returns, ushering in Malvolio, the change in the steward is dramatic. Instead of being "sad and civil," he smiles broadly and continually; he kisses his hand to the Lady Olivia, and instead of being dressed in sober black, he is in yellow stockings with tight cross-garters in a contrasting color. Malvolio keeps on referring to various lines of the letter which he supposes that Olivia wrote to him, but since Olivia did not write the letter, she has no idea what he is talking about. Furthermore, Olivia does not realize that Malvolio is quoting; she assumes his talk to be the ravings of a madman, and she wishes that he would leave her sight and be treated for his madness.
Meanwhile, on the stage, the only one present who does know what Malvolio is referring to is Maria, who is probably behind Malvolio laughing uproariously. Knowing the contents of the letter (since she wrote it), Maria very cunningly asks Malvolio some questions that cause him to continue quoting from the letter; this, of course, heightens the impression that he is raving.
