15-year-old Tracey Berkowitz (Ellen Page) is naked under a tattered shower curtain at the back of a bus, looking for her little brother Sonny, who thinks he's a dog.
Tracey's journey leads us into the dark underbelly of the city, into the emotional cesspool of her home, through the brutality of her high school, the clinical cat and mouse games with her shrink and her soaring fantasies of Billy Zero - her boyfriend and Rock 'n' Roll saviour.
Her travels also put her in contact with the seedier inhabitants of the city. Like Lance, her would-be saviour who ultimately puts her life in jeopardy.
Tracey's stories begin to intertwine truth with lies, and hope with despair as we move closer to the truth of Sonny's disappearance..