Meanwhile, back in Rome. The Cardinal's talking with Ferdinand, Malateste, Pescara, Silvio, and Delio about the new fortifications that the Emperor, Charles V, is setting up in Naples.
It looks like the guys are going to have to do some soldiering.
Count Malateste (the guy Ferdinand mentioned wanting to set the Duchess up with) is showing the fortification plans, while the other guys hang in the background talking smack about his martial abilities—apparently he's not fit to be a soldier.
Trash-talking comes to an end when Bosola comes in to chat with the Cardinal and Ferdinand.
Bosola has shared his newfound info with the brothers, and the Cardinal immediately decides that he'll have the Duchess and her family banished from Ancona.
Ferdinand plans to tell the Duchess's oldest son, the one she had by her first husband, that his mother's been ruining her reputation.
Quick note—keeping track of the Duchess's children can be a little tricky, so take note of the fact that this is the only time we ever hear about this particular kid. Most scholars actually think that Webster meant to edit this son out, because his existence means that Ferdinand won't inherit the Duchess's wealth the way he claims to desire at (4.2.274). Life before Control + Find and Delete was rough, man.