Jason "Igby" Slocumb is a irritable 17-year-old boy, who is fed up with his upscale family’s money and the rest of the world. His name is explained as a family in-joke. As a child, he would blame his toy bear, Digby, for things he had done, mispronouncing it as "Igby". In order to get him to take responsibility for his actions his family would call him Igby whenever he lied. His father suffers from schizophrenia and Igby often contemplates suffering the same consequence. His mother, Mimi is self-absorbed and distant from him. Igbys brother Ollie is described by him to be a “fascist” for studying neo-politics.
Igby figures there must be a better life out there, and he sets out to find it, rebelling against by happily flunking out of several prep schools and soon ends up in a brutal military academy where he gets beaten by the other kids. After escaping and spending time in a Chicago hotel courtesy of his mother's credit card, Igby is sent to New York for the summer to his godfather “D.H” Banes. Igby goes on to work for his godfathers construction company where he meets his heroin addicted trophy wife, Rachel. Rather than return to school, he escapes into the streets of Manhattan, hiding out with Rachel.
Even though his mother is distant from him, Mimi is not unaffected by her rebellious son. Igby is informed by D.H. that his mother Mimi is dying from breast cancer Igby returns to see her. Igby discovers she has arranged to commit suicide with help from Ollie, who sedates her and suffocates her with a plastic bag. Before she dies, Mimi reveals that D.H. is really Igbys father. Igby leaves for L.A in an attempt to finally make a clean