Art is a 47-year-old DEA agent stationed in Mexico, bringing a hardened perspective from his past as a CIA operative in Vietnam. Raised in San Diego by a Mexican mother and an Anglo father, he understands the cultural dynamics of the border. He approaches the War on Drugs with deep idealism, though his methods frequently alienate his colleagues. His absolute dedication to his assignments creates severe strain within his marriage and distances him from his children.

Adán is a highly intelligent college student from a well-connected Sinaloan family. He brings a corporate mindset to the regional drug trade, viewing narcotics trafficking as a logistics and supply chain enterprise rather than a simple criminal racket. He works diligently to maintain a respectable public image and courts women from prestigious families. Beneath his polished exterior, he possesses a pragmatic willingness to do whatever is necessary to protect his blood relatives.

Known to associates as "Tío," Miguel Ángel serves as a high-ranking Sinaloa state policeman and special assistant to the governor. He operates with extreme patience, recognizing that the physical border is more valuable than any individual narcotic product. He leverages his official law enforcement position to eliminate commercial rivals and build a unified smuggling network. He mentors his nephews, gradually pulling them into his expanding commercial empire.

Sean is a teenager from Manhattan who finds himself suddenly embedded in the criminal underworld after protecting a friend from a local enforcer. Raised around Catholic imagery, he internalizes intense guilt over his violent actions. He negotiates his way into the Cimino Crime Family to ensure his own survival and takes control of neighborhood loan-sharking rackets. He harbors a quiet desire for domestic normalcy, yet his lethal efficiency makes him a valuable asset to dangerous men.

Nora is a pragmatic California teenager who learns to leverage her physical attractiveness for financial independence. After her parents divorce, she undergoes rigorous etiquette and educational training to reinvent herself. She operates as a high-class sex worker out of a luxurious San Diego property. She views her profession clinically, prioritizing monetary security and personal agency in an environment heavily controlled by aggressive men.

Father Juan Parada is a courageous Catholic bishop who practices liberation theology in Mexico. He actively defends vulnerable agricultural workers against both state military violence and cartel intimidation. He operates medical clinics with extremely limited supplies and relies on donations to treat the wounded. His unwavering moral clarity provides a stark contrast to the widespread institutional corruption around him.

Raúl is the hot-headed muscle of the Barrera family organization. While his brother focuses on long-term strategy, Raúl handles physical enforcement and intimidation to maintain territorial control. He fully embraces the extravagant, flamboyant lifestyle associated with the drug trade.

Güero is a rising figure in the Sinaloan drug trade and a skilled survivor. He initially works as a loyal protégé for the established regional boss before aligning himself with new power structures. He controls the highly lucrative Baja region bordering California.

John Hobbs is a senior CIA station chief focused on anti-communist geopolitical strategies. He views regional narcotics enforcement as a secondary concern compared to broader Cold War objectives. He willingly partners with illicit organizations to secure funding and arms for rebel forces.

Sal Scachi is a decorated Green Beret colonel who operates as both a CIA asset and a mafia associate. He bridges the gap between American organized crime, Mexican cartels, and covert government programs. He is highly disciplined and forces subordinates to execute targeted assassinations.

Jimmy, commonly known as "Peaches," is a capo in the Cimino Crime Family who aggressively pursues new revenue streams. He defies the direct orders of his mafia superiors by seeking to establish a lucrative cocaine pipeline. He is impulsive and frequently uses physical violence to assert dominance.

O-Bop is a teenager from Hell's Kitchen who enters the criminal underworld to avenge a murdered friend. He is intensely loyal and quick to back up his associates during physical confrontations. He adapts readily to the violent expectations of organized crime.

Althea is Art Keller's wife and the mother of their children. She struggles to maintain a stable family environment while her husband becomes increasingly consumed by his dangerous assignments in Mexico.

Ernie is a dedicated DEA agent who works closely with Art Keller. He risks his personal safety to gather intelligence on the expanding transportation networks moving illicit goods across the border.

Don Pedro is an aging drug lord who has controlled the Sinaloan heroin trade for decades. He operates under traditional codes of conduct and assumes his political bribes guarantee his safety.

Haley manages a high-end San Diego brothel financed by cartel money. She recruits young women and transforms them into highly educated, polished professionals capable of handling dangerous clients.

Lucía is a respectable young woman from a well-bred family. She maintains strict traditional boundaries during her courtship, demanding marriage before intimacy.

Little Peaches is Jimmy Piccone's brother and a trusted associate within their organized crime faction. He participates in high-risk robberies and enforcement actions.

Siobhan is a woman from Belfast who strongly opposes organized crime. She offers her partner a chance at a legitimate, peaceful life outside of the mafia.

Pilar is married to a powerful plaza boss but feels increasingly isolated and unhappy in her marriage. She desperately seeks a way to escape her restricted life.

Fabián is a privileged student who transitions into a lethal enforcer for the Barrera organization. He conducts extremely violent assignments to prove his loyalty.

Tim Taylor is a cautious DEA boss who initially distances himself from aggressive field operations. He adheres to bureaucratic protocols and hesitates to trust agents with intelligence backgrounds.

Gloria is Adán Barrera's daughter. Born with health complications, she requires consistent medical attention. She remains a central vulnerability for her father.

Antonio is an officer with the Mexican federal security directorate. He employs extremely aggressive physical interrogation tactics to extract information from suspects.

Jerry is a middle-aged cocaine dealer from California. He takes a teenager on vacation to a luxury resort, inadvertently exposing her to a recruitment opportunity.