Doctor Pietro Baglioni is one of the few characters in "Rappaccini's Daughter" by Nathaniel Hawthorne. Baglioni is a well respected professor of medicine at the University of Padua and is known as a "physician of eminent repute" throughout Italy. Giovanni, the son of Baglioni's old friend, has come to Padua study with him. Though Baglioni does have flaws in his character, he seems quite pure of heart compared to Doctor Giacomo Rappaccini. In fact, Baglioni serves as a kind of foil for the evil antagonist in this story.
Baglioni recognizes the superior knowledge of his fellow physician but claims he would not want the matter of his own life and death in Rappacini's hands. He tries to warn Giovanni many times about the potential danger of being involved with Rappaccini and insists that Rappaccini "should be held strictly accountable for his failures."
One day Baglioni and Giovanni are walking down the street when Rappaccini passes, and Baglioni makes what turns out to be a deadly accurate observation. He says to Giovanni:
"For some purpose or other, this man of science is making a study of you. I know that look of his! It is the same that coldly illuminates his face as he bends over a bird, a mouse, or a butterfly, which, in pursuance of some experiment, he has killed by the perfume of a flower; a look as deep as Nature itself, but without Nature's warmth of love. Signor Giovanni, I will stake my life upon it, you are the subject of one of Rappaccini's experiments!''
Baglioni is right. While he is kind and professional, Baglioni is also eager to catch his colleague in any kind of unethical act. Baglioni pays the boy an unexpected visit and realizes that Giovanni has undergone some changes (because of the poison, unbeknown to him) and notices a strange fragrance in the room (again, from the poison). The doctor insists that Rappaccini is somehow using Giovanni for some kind of experiment and vows that Rappaccini will not harm the boy.
Baglioni is the one who procures a rare antidote for the poison and gives it to Giovanni (though unfortunately Beatrice is the one who drinks it and it kills her). As a reminder that Baglioni is a man of flaws, Hawthorne places Baglioni in Giovanni's apartment at the end of the story. As the horrific truth is revealed, Baglioni is in the window, looking down and observing everything.
"[I]n a tone of triumph mixed with horror," Baglioni shouts the final words of the story:
"Rappaccini! Rappaccini! and is this the upshot of your experiment!''
Baglioni, like most of us, is a good man with flaws. He is, of course, appalled at the grotesque experiment Rappaccini conducted, but he is ecstatic that the unfeeling doctor has been caught in such an immoral and horrific act.