William Shakespeare 
Twelfth Night 
Or, What You Will

Another case of mistaken identity from the king of the plot twist, Twelfth Night tells the tale of the beautiful young Viola who is separated from her twin brother, Sebastian, when their ship is lost at sea. Believing Sebastian to be dead Viol poses as a man and enters service with the Duke Orisino. When Olivia, the woman that Orisino loves, falls for his messenger "boy" Viola and she in turn falls for the Duke the stage is set for a classic Shakespearean love triangle.