Matt gets expelled from Harvard when security campus finds a stash of cocaine in his dorm, thanks to the coke-head of his roommate. He covers for him since apparently his father is an important politician and is going to be re-elected, so to avoid a family debacle Matt takes the blame. Not finding his journalist father, Matt moves to London with his American sister and her husband Steve. His sister family is Ok; it is her brother in-law, Steve´s old-timer hooligan younger brother Pete, who introduces Matt into the dark side of soccer fanatics, Hooligans.
In the beginning, Pete is not fond of the new family member that knows nothing about football and calls it soccer. After one night at the pub of heavy drinking, he changes his perception about Matt and invites him to watch a football match of West Ham United. On their way back from the football match, Birmingham City Hooligans harass Matt, and Pete and his friends have to intercede just in time before they give Matt the “Chelsea Grin”. Matt soon learns Pete and his friends are members of the GSE (Green Street Elite), a hooligan gang. Soon Matt finds himself enrolled in the gang and as clashes with rival gangs take place, what once was a simple football-cheering contest becomes a bloody street battle with deadly consequences.