South London, 1980. Reggae sound system Ital Lion win through to the finals of a sound clash. Their competitors will be the long established outfit of Jah Shaka. Ital Lion crew include the toaster (rapper) David 'Blue', roadie and driver Beefy, electrical wizard Spark, ladies man 'Lover', leader of the crew Dreadhead, hustler and fixer Errol and Blue's friend, Ronnie, a white guy who accompanies the crew to their dances.

Blue lives with his mother and school dodging younger brother Carlton on an estate in South London. This morning, having failed to persuade his brother to go to school, he arrives late at the garage where his colleague and good friend Ronnie is too stoned to work. Alan, the boss, is unsympathetic to Blue's complaints of overwork and sacks him, amidst a volley of racist insults.

Dreadhead visits a Jamaican entrepreneur called Fat Larry in pursuit of an exclusive import record with which he hopes Ital Lion can beat Jah Shaka. Fat Larry sells him a tune called Warrior Charge. Meanwhile Beefy is humiliated by Jah Shaka's crew and in retaliation he smashes the rear lights of their van.

Beefy and Spark break into a secondary school and steal a tannoy system. Back at a lock-up garage where the crew store their equipment, Spark fixes the tannoy to their sound system. They put on Warrior Charge and dance around to the captivating beat.

Suddenly a furious banging makes its way through the noise. Ronnie is sent to investigate. An irate female neighbour wants them to turn the music down, but when Ronnie winds her up she unleashes a volley of racist abuse at them all.

Lover gets engaged to his girlfriend and at the engagement party, Blue is distressed to find his girlfriend dancing with someone else. Everybody finds a partner to dance with, even Ronnie.

Later that night, as Ital Lion return to the lock-up to offload their equipment, three racist white guys on a balcony throw bottles at them. Ronnie and Blue restrain Beefy who wants to go after them. They eventually calm him down.

Blue wanders the streets alone. A car full of young white men begins to tail him. Blue realises the danger and begins to run. The men leap out of the car and give chase. It seems that Blue runs all night.

In the early morning, Blue looks exhausted as he walks through railway arches. He stumbles into the path of a car that looks similar to the one that was chasing him the night before. However, these are policemen. The police catch Blue, beat him up and arrest him.

Blue's mother puts up the bail for her son, much to the disgust of her live-in boyfriend. Blue goes to the house of his girlfriend, Elaine, but she is not there.

Wandering the streets, Blue witnesses an unpleasant mugging, is rejected by his girlfriend and drops in at a Rastafarian gathering. He goes to the Ital Lion lock-up, to find that the place has been deliberately trashed, the sound system destroyed and racist graffiti daubed on the walls. When the rest of the crew arrive, the gloom deepens and tempers rise. Ronnie is attacked by Beefy and Blue stabs the man he believes responsible for ruining their sound system. Meanwhile Dreadhead locates replacement sound equipment.

At the sound clash, the crowd is on edge because of some earlier violence involving Beefy. Jah Shaka finishes his set, Ital Lion step up to the stage. Since Blue has not arrived, Lover takes over the controls and begins to toast. He doesn't play for long because Blue makes an appearance.

Blue begins a heartfelt rap about life. Outside, scores of police pile out of vans and up the stairs of the concert hall to hammer on the doors that are barricaded against them. Blue defiantly plays on. Eventually, the police break through the door.