Convicted sex offender Lluís asks filmmaker Carles to make a documentary about his life to fix his image. He agrees, expecting an apology, but realizes Gros remains unrepentant. Carles undigs more of Gros's crimes and fights for justice.
After committing a series of multiple murders, a neurologist visits an incarcerated killer, living in exile. She studies him and his brain and discovers the horror that lurks behind his violent impulses.