The melancholy Don John has a conversation with his follower, Conrade. Conrade asks why Don John is acting so gloomy, and advises him to be more patient with his mood. Don John responds that he was “born under Saturn,” (1.3.11) and is unable to hide his feelings. Conrade cautions him to at least have a better attitude toward his brother Don Pedro, who is just beginning to accept him back into his good graces. But Don John refuses, saying that he would rather be himself, and hated by everyone, than falsely friendly. Because of this honesty in his behavior, he calls himself a “plain-dealing villain.” (1.3.32)
It was once believed that people born under the planet Saturn were naturally gloomy and slow to change their moods. Don Pedro’s “saturnine” personality contrasts with those of almost every other character in the play. Where he is melancholy and unchanging, they are lively and experience huge changes over the course of the story. His “plain-dealing,” villainy is the opposite of the good natured tricks played by the other characters, who have the best intentions in mind.
Another of Don John’s followers, Borachio, arrives to give him some news. While eavesdropping from behind an arras (a kind of tapestry), Borachio learned of Don Pedro’s intention to disguise himself and woo Hero for Claudio. Don John complains that Claudio “has all the glory of [his] overthrow,” (1.3.67) in battle, and wants to get even with him by destroying the marriage proposal. He imagines that Don Pedro and the others are enjoying themselves even more because of his own unhappiness. Along with Conrade and Borachio, Don John heads out to supper at Leonato’s, hoping that he might be able to screw something up either there, or at the masked dance after.
Eavesdropping is the dominant plot device in the play. Almost everything happens because an eavesdropper heard about it. This is common throughout Shakespeare: Hamlet kills Polonius, for instance, after finding him eavesdropping behind an arras. The reason for Don John’s unhappiness is revealed: he was defeated in battle by his brother Don Pedro, whom he was trying to overthrow. Since Claudio has been celebrated for his role in the victory, he’s an excellent victim for Don John’s evil tricks.