The drug war on Avon Street intensifies as external threats move in to take control of the territory. The group is forced to move their operations elsewhere to survive while trying to maintain their grip on the streets. Paul Rinaldi begins to spiral mentally.
Marcus and the crew visit a critically injured Corey at an underground doctor's clinic to keep him off the police radar, where they learn that Vaughn has been killed. Meanwhile, a severely beaten Mac stubbornly continues his hunt for Sal Pagano, but is forced to abandon Avon Street and retreat to a new hiding spot within Newark as the Paganos take total control of Avon Street. Corey’s anxious parents are brought in to see Corey and reluctantly accept a payoff from Mac’s men to keep quiet and not go to the police, though the deal is not without tension, as they struggle to process their son's condition.
Mac brings Marcus and Reggie to his new base of operations outside Avon, forcing the boys to drop out of school and abandon their homes. They tell their families they will be back soon and make them promise that they won't tell the police. While the boys struggle to adapt to their sudden life on the run, Mac begins a search for a new chemist to replace Vaughn. Corey's parents visit him in the underground clinic and are bribed to say nothing about the drug business. Corey's father is hesitant, but takes the money and stays quiet.
Paul’s obsession destroys his personal life, culminating in a brutal bar fight with the chief of police that gets him fired. Meanwhile, Mac hires an unstable new chemist and orders Daniel to become the chemists apprentice, while Marcus finds a job for a woman named Nicole to handle logistics and spy on Pagano territory.
A disgraced Paul spirals into isolation, living as a drunken mess after losing his badge and family. Meanwhile, Marcus faces intense drama over the phone with an increasingly stressed Desmond, and Reggie finds himself developing feelings for Nicole, complicating the crew's focus during their exile. Daniel denies Mac's order for him to help the chemist, instead staying in Avon, away from the drug business, with his little brother Mikey.
As Mac and Reggie hit the streets of Newark to distribute their new product, Marcus is forced to return to Avon Street after a desperate Desmond threatens to call the police. Meanwhile, an encounter with a young child in the drug business forces Reggie to confront the dark reality of his lifestyle. Reggie gives the child money and food, telling him not to tell anybody. After he leaves the place with the child he cries silently to himself, knowing the child may not live a long life.
Reggie and Nicole officially begin dating, offering a brief break from the drug business. Meanwhile, a completely unhinged Paul restarts his investigation with a new mindset, willing to kill anyone in his way. Back in Avon, Marcus confesses the truth about the drug empire to his distraught brother Desmond, promising that he will make money for the family. Desmond remains silent, though he is affected greatly.
Corey finally wakes up from his coma, with Daniel arriving to catch him up on what's happened to the crew. Now backed by a decent stash of drug money, the crew prepares to reclaim Avon Street until a heated argument turns into a fistfight between Marcus and Reggie when Marcus accuses Reggie of prioritizing Nicole over the business. Mac breaks up the fight. Meanwhile, a ruthless Paul invades Avon Street alone, kicking off a bloody gunfight between the Pagano's without knowing who they even are. A small outpost of Pagano's are massacred by Paul, who then flees back home.
Mac’s crew returns to Avon Street only to find the Pagano outpost already slaughtered. Before they can process the confusion, a massive Pagano reinforcement squad ambushes them, triggering a chaotic shootout where Reggie rushes Nicole to safety before joining Marcus in the fight. With a recovered Corey arriving just in time to turn the tide, the Paganos are decimated, leaving a defeated Sal Pagano to be brutally executed by Mac with a broken street sign pole, officially ending the war.
An empty Mac after achieving his revenge reclaims his throne over Newark but coldly dismisses a concerned Marcus when he asks about what to do next. Seeking retribution for their wiped-out allies, the furious Capos kidnap and violently beat Marcus at their safehouse. With Reggie and Corey busy clearing bodies from the aftermath of the street war, and Mac occupied in a meeting with Deuce Sevens leader Stacks, Daniel is the only one left to answer Marcus’s desperate call. After Marcus manages to kill most of his captors, Daniel arrives just in time to shoot the final Capo holding a gun to Marcus's head, leaving Daniel deeply traumatized having his first kill and ruining his long run of innocence as they escape.
Marcus gathers the boys to decide on whether to stay with Mac or not. The Capo's cause major damage to a base of operations for the Deuce Sevens, almost killing the leader Stacks. Paul speaks to his children and reflects on how he has changed from when he first started the investigation, realising how his life has fallen. Marcus confronts Mac, wanting to have a normal conversation. Mac, having changed after killing Sal Pagano, attacks Marcus. The two fight until they're almost dead. Just as Mac is about to strangle Marcus to death, Marcus fires his gun from his hip into Mac's stomach, killing him in self defence.
Following Mac's death, Corey is tasked with getting rid of the body. Reggie goes silent, not responding to his phone as he talks to his abusive father, who lays on the verge of death after falling sick while Reggie was gone. Reggie, knowing how much pain his father has caused him and realising he cant hang onto his father like his mother when she had cancer, tearfully pulls the plug on his deathbed, killing him. Stacks, the leader of the Deuce Sevens, is furious after finding out Marcus killed Mac, as they were allies. Stacks and his members figure out who Marcus is close to, and go to his house. They brutally execute Desmond.
The rest of Marcus' crew are forced to engage in war with the Deuce Seven's as Paul begins to move toward them. Marcus finds Desmond's body. Enraged, Marcus heads over to kill Stacks. As Stacks prepares to execute Reggie during a street standoff, Marcus runs his car into Stacks, crushing his legs against a wall. As Stacks crawls helplessly on the pavement, his legs broken, he is shot and killed by a tearful Marcus as his friends watch. With the Deuce Seven's leader dead and the conflict losing its momentum, the remaining gang members scatter away, allowing the crew to finally retreat and head home. Later, Marcus sits alone on the doorstep of his new base. Paul confronts him, his gun drawn. Marcus recognizes him and draws his own; a savage brawl ensues. They trade gunfire until empty, then fight with fists. Marcus defeats Paul, both of them bloodied. As Paul collapses, Marcus lies beside him a moment before leaving, assuming he is dead.