We're introduced to two new characters, the schoolmaster Holofernes and Sir Nathaniel, the curate (country preacher).
Holofernes is learnèd and enjoys talking. If he hasn't said something six different ways, he hasn't said it at all.
Nathaniel seems to be a fan of this sort of thing. He complements the schoolmaster's speech but disagrees with his assessment of the kill.
Dull gets in on the disagreement and Holofernes is offended by his ignorance.
Nathaniel charitably asks Holofernes to accept this dolt – after all it would be an insult to the school to see him in it. The three exchange a few more riddles until Holofernes, inspired, offers "an extemporal epitaph on the death of the deer" (4.2.18).
Holofernes has at it, delivering a little speech full of alliteration and wordplay. Nathaniel is impressed; Dull not so much. They are interrupted by Costard and Jaquenetta, who want them to read her letter from Don Armado.
Well of course it's the wrong one! Nathaniel reads aloud Berowne's letter to Rosaline.
Holofernes looks it over and gives it a big fat shrug. Nothing special, in his opinion. And was it really meant for Jaquenetta?
She thinks so. But Holofernes reads the address and sees "Rosaline." He advises Jaquenetta to take the letter to the King. She exits with Costard.
Holofernes insults Berowne's letter a bit more and invites Nathaniel and Dull to dinner. They all exit.