As Harry Mitchel (Ray Winstone), freshly released from prison after being convicted of grievous bodily harm under mysterious circumstances, steps into a realm of possibilities. His former associate, Billy Norton (Colin Farrell), reaches out with an olive branch and a tempting offer to reconnect with the luxuries of life—on the condition that Mitchel serves his criminal overlord. Yet, before he can settle into this uncertain path, Mitchel encounters Penny, a damsel in distress, and instinctively comes to her aid against a pack of muggers.
As he wades through the murky waters of crime and treachery, Billy emphasizes the necessity of aligning with their boss. At a raucous "welcome back" party, Mitchel's life takes an unexpected turn upon meeting Charlotte (Keira Knightley), an enigmatic and reclusive actress whose life is under constant media scrutiny.
With Billy's blessing, he reconnects with Joe, a blind Big Issue vendor, who cryptically imparts wisdom regarding the significance of self-defense. The next day, Mitchel finds himself deeply intertwined with Charlotte's tumultuous life, surrounded by opulence and the ever-watchful eyes of the press. Introduced to Jordan, Charlotte's loyal protector, Mitchel is taken on a tour of her lavish mansion, complete with exquisite Francis Bacon-inspired paintings and an impressive collection of her ex-husband Tim's prized automobiles.
However, corruption rears its ugly head when Detective Bailey pays a visit, warning Mitchel to distance himself from Billy. Ignoring this caution proves to be a perilous choice when Joe is violently assaulted by two teenage footballers, and later, one of them steals Joe's trusted knife.
As Joe fights for his life in the hospital, Dr. Sanji Raju relays Joe's dying wish to Mitchel—to avenge the brutal assault. Sensing an opportunity, Billy fills Mitchel in on the intricacies of Tim's coveted car collection and their boss's appetite for it. The sobering reality of mortality hits hard during Joe's funeral, coinciding with Dr. Raju's budding affection for Briony.
Determined to unearth the identities of Joe's attackers, Mitchel recruits Danny for a dangerous nighttime quest, which culminates in a shocking kidnapping orchestrated by Billy and Rob Gant. The pressure mounts as Charlotte attempts to evade the paparazzi, retreating to her serene countryside abode, where she unveils a haunting secret—a dark past involving a traumatic drug overdose in Italy, intertwined with a malevolent act by a drug-fueled assailant now existing in a vegetative state.
Meanwhile, Gant threatens Detective Bailey to keep his distance from Mitchel, while the darkness of Gant's nature emerges during a tense meeting in a secluded garage. Gant reveals his true character by heartlessly targeting an unsuspecting black man, assuming he is linked to the Nation of Islam, prompting Mitchel to bravely intervene. Confronting Gant, Mitchel refuses to be manipulated into complicity, declaring that he must steer clear of his life.
As emotions intensify, Charlotte confesses her love for Mitchel, leaving him to grapple with his burgeoning feelings amidst the weight of her chilling revelations. Gant soon places Mitchel on a merciless mission to collect money from various locales in South London—a challenging test of his loyalty and moral compass.
In his journey, Mitchel learns that one of Gant’s targets is a promising young footballer, which draws him deeper into a perilous web orchestrated by Gant, who threatens those dear to him if he does not comply. Refusing to surrender, Mitchel tracks down the footballer, realizing Gant's malicious reach extends to Charlotte's husband as well.
Desperate to save his sister from Gant's clutches, Mitchel attempts to convince her to leave the country, offering her a train ticket and financial support, but she stubbornly rejects his pleas. The fallout is swift, as both she and Dr. Raju fall victim to Gant's ruthless nature.
Amidst the chaos, Mitchel discovers Billy's lifeless body outside Charlotte's home, a somber testament to the cost of their relentless struggle. Together with Jordan, he seeks to confront the lurking threat of Storbor, a Bosnian figure whose sinister motivations are alarming. Their path leads them to a nightclub where they encounter Whiteboy, a danger from Billy's party, and a tense showdown unfolds.
In a climactic moment, Mitchel faces Gant, seemingly narrowing in on a decisive victory. However, as he strides towards freedom, a twist of fate strikes—one of the survivors he previously spared exacts revenge, delivering a fatal blow that leaves Mitchel bleeding and vulnerable on the unforgiving pavement, a stark reminder of the brutal world he tried to escape.
