Jimmy (Harvey Keitel) lives a double life; in one he is a talented pianist, in the other he is a violent debt collector for his father Ben (Michael V. Gazzo). Jimmy trains to play professionally and wants to leave his father's life of crime behind. However, on the day of his big audition, he chokes due to heavy stage fright. He later relates to his mother that he can play perfectly alone, but around people he freezes.
Jimmy tries to collect on Riccamonza (Tony Sirico) a mobster who owes Ben $22,000 but has difficultly getting the guy to pay up. Ben tells Jimmy he must kill him but Jimmy says he can't. Not much later, Riccamonza calls Jimmy and tells him "it's done" and warns him not to do anything further. Jimmy rushes to his father's apartment and finds him murdered.
With nothing to lose, Jimmy runs to the club Riccamonza spends time at and jumps him (as only his associates had seen Jimmy face to face) engaging in a brutal fight that ends with Jimmy shooting him in the eye twice.
The film ends with Jimmy at his piano naked, staring out of the window. He turns to the camera with a haunted look on his face. With his dream of playing music destroyed, his father murdered, and now knowing his true, violent self, Jimmy literally has nothing.
Thanks Tim (Spectre)!