Antonio asks Delio what he thinks the chances are of him making peace with the Duchess's brothers.
"Nada, buddy—they're only making friendly overtures so they can trap you. Also, you should look out for the Marquis of Pescara; he's not a bad guy, but if your lands are confiscated they'd fall to him, so he's probably got it in for you."
Speak of the devil, Pescara himself happens along, and Delio goes forward to test whether or not he can be trusted while Antonio hides.
Delio asks a favor of Pescara—namely, that Pescara fork over Antonio's lands to him.
Pescara refuses, saying that since they're Antonio's lands, he can't give them away, and Delio can't take them. Sounds like maybe this Pescara's a good guy.
Enter Julia, the Cardinal's mistress, who asks Pescara the same thing, on behalf of the Cardinal.
Pescara changes tune in the blink of an eye: "Sure, by all means, take Antonio's lands, anything for my bestest friend the Cardinal!"
After Julia leaves, Delio turns and asks Pescara what the heck just happened.
Pescara's response? "Well, you're my friend, and Antonio's lands were obviously being unjustly seized, and I couldn't give my friend illegal land, now could I? So I gave it to somebody I don't like, the Cardinal." Yeah. That's really what he says.
This seems like a pretty lame excuse to us, but Antonio apparently buys it, and proposes to Delio that he go in secret to the Cardinal and confront him in his bedroom, just like Ferdinand did to the Duchess in Act 3, Scene 2.
He thinks that if he can face the Cardinal and just be straight up about how much he wants to reconcile, the Cardinal will see reason and they can make peace.