Tommy Johnson is a member of a violent Chelsea hooligan firm. His friends and fellow hooligans include Rod King, the hot-tempered Billy Bright, and impulsive younger members Zeberdee and Raff. Tommy spends his days drinking, using drugs, womanising and fighting, much to the disappointment of his grandfather Bill Farrell, a pensioner and veteran who plans to move to Australia with his best friend Albert Moss.
Tommy has an epiphany about his lifestyle during a fight with the Tottenham hooligan firm. Tommy, Billy and Rod are arrested for assaulting two Stoke City fans whilst travelling to an away match. These actions draw the fury of Harris, the leader of the Chelsea firm, whose attempts to keep order are thwarted by Billy's aggressive outbursts.
Tommy, Billy and Rod have to attend court in order to answer for their behaviour. Rod begins a relationship with Tamara, the court clerk present at their court hearing, and she pressures him to skip his weekend meets. Zeberdee and his friend Raff accidentally burgle Billy's house and are forced to stand in his living room, whilst Billy's children throw darts at them as punishment, with one of the children kicking Zeberdee in his loins. Billy deals with his increasing loneliness after he overhears Harris discussing his irrelevance and unreliability. Bill Farrell's plan to retire to Australia are postponed, when Albert dies the night before they are to leave.
Early in the film, Tommy is caught and held hostage by the brother of Sian, a girl he picked up at a club. He is saved when Rod hits the man on the head with a cricket bat and they both run away from the house. Sian's brother turns out to also be the brother of the rival Millwall firm's leader, Fred, who then hunts Tommy down throughout the entire film. The film culminates in a pitched battle between the Chelsea and Millwall firms. Rod (after a few espressos and a line of cocaine), leaves a dinner with Tamara's parents after offending them, and attends the "meet", much to the joy of Tommy who is glad that his friend showed up for the meet. Tommy is severely beaten by Fred and a group of Millwall hooligans, with a brick being smashed into his face, and ends up in the hospital with Bill, who, in the meantime, has suffered a heart attack after confronting Zeberdee and Raff on the bus.
At the end of the film, a crippled Tommy decides that his place is at the firm with his friends, Bill gets cured and moves to Australia and Billy Bright is incarcerated for seven years in HMP Full Sutton after being arrested at the Millwall meet (whilst saving Harris from being arrested). Zeberdee is killed by a drug dealer, whom he and Raff had previously mugged, fulfilling a recurring nightmare that tormented Tommy throughout the film. In a pre-credits slideshow, Tommy is shown to have since moved on to watching Rugby. However, this is only a joke and he has not actually started to watch rugby.
