How was the confusion of the mistaken identity overcome in Twelfth Night?

The action turns to Malvolio's condition; his letter is read, and his condition explained. Malvolio is upset at his mistreatment, and Olivia attempts to smooth things over; Fabian explains his, Sir Toby's, and Maria's part in Malvolio's torment. Then, Feste inflames Malvolio's anger, and he leaves, in a huff.

Orsino pronounces that happiness will stay with all of them, and that his marriage to Viola will soon be performed. Feste closes the play with a song about "the wind and the rain," a reminder that even great happiness is not safe from life's storms.