Teenage drug runner Cedric Beauville finds himself in a perilous situation when he is caught by the Royal Canadian Mounted Police at the Canada-United States border while carrying a significant quantity of illicit Fentanyl pills. In a parallel narrative, Dr. Tyrone Brower (Gary Oldman), a research scientist from Everett University, is hired by Northlight Pharmaceuticals to conduct a study on their upcoming product, Klaralon. This new drug is being heralded as a revolutionary, non-addictive painkiller, meant to replace Oxycodone. However, Brower's research unveils troubling findings: while Klaralon may appear non-addictive during its initial week of use, it dramatically increases in addictiveness thereafter, nearly tripling its potential compared to Oxycodone.
Recognizing the serious risks this poses to public health, Brower advises Northlight to postpone the drug's release for extensive further testing. Unfortunately, the company is resistant, and Dr. Bill Simons (Luke Evans), a board member, attempts to sway Brower with a hefty research grant of $780,000, but Brower stands firm. Faced with mounting pressure from his department head, Geoff Talbot (Greg Kinnear), Brower continues to refuse, prompting Northlight to undermine his reputation publicly, and resulting in the revocation of his tenure at the university.
As Brower grapples with the moral dilemma, he takes the bold step of becoming a whistleblower, reaching out to the FDA and connecting with investigator Ben Walker (Scott Mescudi). Meanwhile, in a separate storyline, Detroit DEA agent Jake Kelly (Armie Hammer) is on the ground, infiltrating two significant Fentanyl drug cartels: one steered by the Armenian Mafia and the other run by the Montreal-based kingpin Claude 'Mother' Veroche (Guy Nadon). Intending to orchestrate a simultaneous bust, Kelly is fueled by personal stakes—his younger sister, Emmie (Lily-Rose Melody Depp), is ensnared in her own battle with heroin addiction.
Tensions build when Mother learns of Cedric's arrest, leading him to eliminate the young runner, fearing he might squeal. Amidst this chaos, Kelly reports that the American mafia exploits homeless individuals to funnel them into clinics where doctors freely prescribe Oxycodone—all of this while the cartels intensify their push for Fentanyl, a drug significantly more potent than heroin.
Under pressure to expedite cartel meetings, Supervisor Garrett (Michelle Rodriguez) decreases Kelly's timeline for the operation. As the plot thickens, Claire Reimann (Evangeline Lilly), an architect grappling with her own demons, becomes distraught when her son David fails to return from hockey practice, only to discover he died from an overdose of Oxycodone. Convinced he never faced drug issues, Claire hires a private investigator who reveals that her son was murdered—his death a tragic consequence of the drug underworld in which he was reluctantly entangled.
Determined to seek justice for her son, Claire embarks on a perilous journey into the heart of the drug trade. This quest leads her to Montreal, where she acquires information about Mother and secures an untraceable ghost gun, preparing to confront those responsible. Kelly, aware of Claire's dangerous path, intercepts her outside La Marina, aiming to protect her rather than arrest her.
The anticipated cartel meeting is set in motion, monitored by a meticulous joint task force; however, a minor blunder leads to a violent shootout, resulting in the death of Kelly's partner. In the aftermath, both U.S. and Canadian agencies decide to cease their pursuit of Mother and the Armenians, prompting Kelly to take matters into his own hands. Learning of Mother's intentions to flee, Kelly rushes to the port only to find Claire there, who confronts Mother in a tense showdown.
As both sides clash, the scenario spirals, leading to the apparent demise of Mother, with Kelly creatively covering up the incident to protect Claire. Back on the corporate front, Brower's dedication to the truth culminates in a public reveal of Northlight's deceptive practices, despite the company’s desperate last attempts to sway him. Energized by his integrity, he secures a new position at the University of Michigan, where he is seen sharing his insights with an eager audience, underscoring the power of truth against corporate malfeasance.
