He says to Giovanni that Rappaccini is a very skilled man, but there is things about him that are weird. When they meet later, Pietro tells him that he afraid for him, because he doesn't trust Rappacini and even his daughter. Days after, Pietro tells him that this bottle will save him from the poison of Rappacini. Finally, he tells Rappacini that the poison his created was to powerful to only destroy itself, it took his girl with it