Fra Lippo Lippi, which basically means "Brother" Lippo Lippi, is a monk who has been up to some rather un-monk-like activities. The guardsmen of the powerful (and don't forget rich) house of Medici catch him out, partying it up on the streets, and so they roughly interrogate him.
Being drunk, Lippo is only too happy to give them the story. And by that, we mean his entire life's story. He starts from the time he was a poor orphan, literally duking it out with dogs in the streets for their leftovers. He grows into an artistically-gifted monk that at least has a stable roof over his head and food in his belly.
The Prior and the other higher-up monks don't like his art, though. They think it's too realistic, that it doesn't give proper attention to what's really important: the soul and glorification of God. Needless to say, Lippo doesn't agree. To show that he's a rebel with a cause, he sneaks out at night and parties, enjoying the company of women of ill repute.
Throughout his drunken ramblings, Lippo tosses in some of his own philosophies about art and its purpose, and how his ideas differ from those of the Church and even his powerful patron, Cosimo Medici. It's hard to please both himself and his two very different masters, but he's working on a painting that will do just that—if he's able to pull it off.