"She waited for the affair to end, for Deborah to break Pranab Kaku’s heart and for him to return to us, scarred and pentinent.” Having someone close to us slowly driff away if painful and even more so when that person is drifting for another person.  Lahiri wants to relate the expirance the emotion the heat ache even the bitterness. She wants to appeal the the little green monstor inside of us that wants others to feel our pain. Yet also she wants us relate to the broken heart. The broken hearted are always the most empathic, this may be a reason the rhetor included how Pranab Kaku may have felt or to describe to our darker side the deep level of pain that would be inflicted on him.