Don John (Don Pedro’s illegitimate brother) meets with Conrade (his attendant).
Don John is being a his usual negative self, and Conrade tries to placate him with platitudes. (How’s that for vocabulary enrichment!)
Don John wonders how Conrade can be a regular Charlie of the Chipper Brigade when he’s supposed to be born under Saturn (which was thought to be the planet farthest from the sun, and thus the coldest and grumpiest planet to be born under). Don John doesn’t bother with silver-linings; when he’s cranky, he’s not going to hide it.
Don John says he eats only when he’s hungry, sleeps only when he’s drowsy, and isn’t going dance like he’s some clown when he’s not feeling like a dancing clown. (Well fine, he doesn’t say that last bit, but you get the point.)
Conrade’s pretty serious though, and says Don John has to get his attitude in check, because he’s still treading on delicate ground. Don John only recently reconciled with his brother, Don Pedro, but the reconciliation is worthless if Don John can’t get it together and stop acting like a villain.
Like any good villain, Don John points out that he acts like a villain because he is a villain, and he doesn’t care whether he’s hated.
Don John notes that while he seems to be in the good graces of his brother, he’s actually more like a muzzled dog tied to a block than a trusted guy.
Don John doesn’t deny, though, that his brother’s precautions are reasonable ones, as he would like to do some mischief as soon as he gets the chance. (Plotline of the play = Don John’s chance to do mischief.)
In the meantime, Don John isn’t going to join the "Vote For Don Pedro" squad, no matter how much people try to convince him it’s a good idea.
Borachio enters and delivers to Don John news of an impending marriage.
Borachio was perfuming a smelly room by burning some aromatic substance, when he heard Claudio and Don Pedro approach, deep in conversation.
Borachio got the gist of the conversation correctly (unlike Antonio’s man) about Don Pedro’s plan to court Hero on Claudio’s behalf. This is kind of a Tarantino approach to the wooing of Hero, which we now see is the focus of like 8 million schemes from her dad, Don John, and of course Claudio and Don Pedro.
Don John is elated to hear news of this little plan between Don Pedro and Claudio, especially as he blames Claudio for playing a large part in overthrowing him in a vaguely-mentioned rebellion. (Some scholars think this alludes to the battle that took place before the play’s first scene, which may have been a contest between Don Pedro and Don John for power.)
The men exit, plotting their mischief, though we think Shakespeare may be gearing up with a lot of sardoodledom (that's a fun theater word for melodrama).