The film opens with Counselor (Michael Fassbender) and his girlfriend Laura (Penélope Cruz) in an intimate moment, juxtaposed against a scene of Mexicans clandestinely hiding cocaine within a sewage truck. Counselor soon travels to Amsterdam, ostensibly for business, but his true intent is to purchase a diamond ring for Laura, as he plans to propose.
Upon arriving, Counselor encounters Reiner (Javier Bardem), who persuades him to enter the risky world of drug trafficking in pursuit of wealth. Counselor decides to partner with Reiner and arranges a meeting with Westray (Brad Pitt), Reiner's business associate, to kickstart the deal. During the meeting, Westray warns Counselor about the grave dangers of aligning with the Mexican cartel, yet Counselor remains undeterred.
Later, Counselor visits Ruth (Rosie Perez), a client in prison, who shares that her son, Richard (Richard Cabral), is incarcerated after being caught with a significant amount of cash. Although Ruth is unaware of the source of the money, Counselor promises to assist her son. Unbeknownst to him, Richard possesses a crucial engine component hidden in his helmet, vital to the operation of the cocaine-laden sewage truck.
As the plot unfolds, Reiner confides in Counselor about his girlfriend, Malkina (Cameron Diaz), revealing his conflicting emotions of love and fear due to her erratic behavior. In a dark turn of events, Malkina is shown conspiring with "the Wireman" (Sam Spruell), intending to pursue Richard for the stolen component.
In a harrowing scene, Wireman brutally murders Richard and seizes the component. Later, in a confrontation with men posing as police, Wireman and his partner engage in a firefight, with tragic consequences for all involved. This escalating violence leads the cartel to target Counselor, whom they believe played a role in the heist due to his connection with Richard.
The cartel's retaliation sees Laura taken hostage, further spiraling Counselor into despair. Meanwhile, Reiner meets a violent end when the cartel retaliates against him, as Malkina, driven by financial desperation, pursues a deal with Westray. She cleverly manipulates her way into Westray's confidence, obtaining vital information through deception.
With the tension rising, Malkina orchestrates a chilling assassination using a device designed for cruel efficiency, demonstrating her ruthless ambition. As her plans unfold, she contemplates a new life in Hong Kong, leaving chaos in her wake. Frantically, Counselor seeks assistance from a cartel higher-up, Jefe (Rubén Blades), only to be met with disdain as Jefe implies that Counselor sealed his fate by entering the deadly game of drug trafficking.
In a haunting climax, Counselor receives a shocking DVD with the word "Hola!"—a harbinger of his worst fears as it depicts the brutal fate of Laura at the cartel's hands, showcasing the terrifying consequences of his choices.
