Dennis "D" Campbell [Aml Ameen] lives with his peace-loving brother Jerry Dread in 1973 West Kingston, Jamaica. D loves a local schoolgirl named Yvonne [Naomi Ackie], but their relationship is strained by a brutal gang war between the Tappas, led by Skeeter, and the Spicers, led by King Fox. Tired of the ongoing violence tearing through the streets, Jerry Dread arranges a DJ session intended to bridge the two territories and foster peace. The plan collapses when Jerry is shot and killed by Clancy Hibbert, one of D's classmates and an aspiring gang member, setting a vendetta that will haunt D for years.
By 1983, an adult D has become a hardened enforcer for King Fox [Sheldon Shepherd], who operates as both a record producer and a drug lord. After bungling one of Fox's drug deals because of his volatile temperament, D is sent to Hackney, London, to deliver a package of cocaine to Rico Grimes, a White Jamaican gangster. D arrives with caution, hesitates to make the delivery after Rico flippantly insults his late brother, and escapes Rico's nightclub with the cocaine in hand, reuniting with Yvonne. Yvonne had fled to London with her and D's daughter Vanessa to escape Kingston's violence; she does not welcome D's presence but agrees to let him stay. While in London, D grows suspicious that Clancy—the man who killed his brother—is also in the city.
A group of youths burgles Yvonne's flat while D is there, hoping to steal the cocaine he still has. After stopping them, D is directed by the youths to a potential buyer—the Turkish crime lord. Using the money he earns from the sale, D tries to provide Yvonne and Vanessa with a better life. He also uses the funds to help the youths fix their sound system and eventually joins them for gigs, letting the music temper the violence that has defined his life.
Not long after, D is recognized and ambushed by Rico's men. Yvonne kicks him out after her daughter is fake-kidnapped. D goes to Rico's nightclub to return the money and is spared only because of Fox's influence.
Directionless, D returns to his last remaining objective: finding Clancy in hopes of avenging his brother. After being pointed in the right direction by Sticks, one of the DJs, D confronts Clancy at his home. He is then ambushed by Rico's lieutenants, resulting in Clancy's escape and Sticks' death.
Yvonne seeks out Clancy and learns that Fox has a hand in Jerry's death. That night, as D takes Sticks' place in a DJ group for a concert at Rico's nightclub, Yvonne tells him what Clancy shared and begs him not to go, but he remains resolute. At the same time, King Fox arrives in London to meet with Rico and smooth over the tensions. During the DJ session, Rico insults Fox and threatens to kill D himself, prompting D to strangle Rico in self-defense.
King Fox later confronts D in a hallway, offering reassurance about Clancy's claims. Clancy then ambushes them both, claiming that Fox had hired him that fateful night, forcing D to kill him in self-defense. An injured Fox inadvertently reveals his role in Jerry's death, prompting D to question him. King Fox confirms the truth: Jerry wasn't the intended target that night—Skeeter was—and Clancy's shot hit Jerry by mistake. Enraged by the revelation, D kills King Fox. The ghost of Jerry, a constant presence in D's conscience, fades away. In a final flash-forward that leads to Fox's execution, D and Yvonne are shown happily together with their two children.
