The Jew of Malta Act 4, Scene 3 Summary

Barabas is venting about the audacity of Ithamore's first letter when Pilia-Borza returns, bearing the second letter, this time demanding 500 crowns.
Barabas is, predictably, not happy about this turn of events.
Obviously he wants to kill Pilia-Borza, but he holds off for the meantime. And he makes it clear that he knows Pilia-Borza has stolen from him before.
Pilia-Borza doesn't care, though, because he has enough information to get Barabas executed.
Barabas figures out that Ithamore has betrayed him, and grudgingly gives Pilia-Borza the money.
Pilia-Borza leaves, with Barabas fuming about how he's going to kill Pilia-Borza and Ithamore.
He plans to show up at Bellamira's house (where Ithamore is staying) in disguise.