Journalism student Matt Buckner (Elijah Wood) has been expelled from Harvard for a crime he didn't commit. His promising career ended and his future looking bleak, he heads for London to seek refuge with his married sister Shannon (Claire Forlani) and her husband Steve (Marc Warren).

Steve introduces Matt to his younger brother Pete (Charlie Hunnam) and, through their friendship, Matt enters the world of football fanaticism and the secrecy and intrigue of the football firm.

Pete Dunham and his close knit group of friends make up the Green Street Elite (GSE), a hard core group of West Ham United supporters – and one of the toughest London football firms. All the football clubs have a firm and they all have one aim – to be the most feared and respected mob in the country - no matter what it takes. As Pete explains 'West Ham's football is mediocre, but our firm's top notch and everyone knows it… it's really about reputation – humiliating the other mob by beating them in a row or doing things that other firms get to hear about.' Matt is not only drawn into the sheer excitement of the game of football itself, but also the brotherhood and loyalty of life inside the GSE. The buzz that violence brings to him produces a sense of power that he has never before experienced.

But Matt has been sparring with the truth about his past life and not every member of the firm considers him a 'brother'. Bovver (Leo Gregory), resents the presence of the outsider and his own apparent demotion within the ranks of the GSE. His continuing distrust and dislike of Matt creates a powder keg of jealousy and emotion that's just searching for an opportunity to blow.

When Bovver discovers hidden information about Matt it sets off a devastating chain of events that tests friendship, loyalty, honor and determination in battle. Tragic consequences force Matt to acknowledge the cost of his actions and the painful lessons learned lead him to re-evaluate his future.