Teresa, the expectant adolescent daughter of a formidable Mexican crime lord known as El Jefe (which translates to 'The Boss'), is called before her father for an intense interrogation regarding the identity of her unborn child’s father. Under extreme duress, she names Alfredo Garcia, who had been groomed by El Jefe to become his successor. This revelation sparks El Jefe’s wrath, leading him to place a staggering $1 million bounty on whoever can "bring me the head of Alfredo Garcia."
The hunt for Garcia stretches over two months. In the heart of Mexico City, two hitmen dressed in business suits, Sappensly and Quill, step into a local bar where they encounter Bennie, a retired U.S. Army officer who now struggles as a piano player and bar manager. In their quest for information regarding Garcia, the hitmen question Bennie, who feigns ignorance, claiming that the name rings a bell but doesn’t know the man personally.
However, it becomes clear that the entire bar is aware of Garcia’s notorious reputation; they simply don’t know where to find him. Bennie later meets with his girlfriend, Elita, a maid at a rundown motel, who candidly admits to having been unfaithful with Garcia. Despite her affection for Bennie, she discloses that she is aware of Garcia’s tragic end in a drunk-driving accident just the week prior.
In a twist of fate, Bennie approaches Sappensly and Quill in the hotel room of their employer, Max, who is an associate of El Jefe. He brokered a deal worth $10,000 for Garcia's head, along with a $200 advance for his expenses. Persuading Elita to accompany him on a trip to pay respects at Garcia’s grave, Bennie assures her it is merely for proof of his demise, a ploy to secure their relationship's safety.
Bennie pops the question, assuring Elita that life will get better, leading her to eventually leave her cleaning job. Yet Elita cautions him against disrupting their current stable life. During a picnic, their tranquility is shattered when two bikers confront them, brandishing weapons. One biker takes Elita aside and after a violent encounter, she shares a kiss with him. Bennie retaliates, knocking out the second biker and shooting the first dead while saving Elita from further harm.
Devastated by the day’s events, Bennie reveals to Elita his twisted plan to decapitate Garcia's corpse and profit from it. Shocked, Elita pleads with him to abandon the plan and return to the relative safety of Mexico City. Despite her concerns, Bennie insists they marry at the church near Garcia’s resting place. While visiting the grave, tragedy strikes when Bennie is attacked from behind and rendered unconscious. Upon regaining his senses, he finds himself half-buried in the grave and discovers Elita lifeless beside him, with Garcia’s body grotesquely decapitated.
After learning from locals that his assailants are fugitives in a station wagon, Bennie confronts them once they experience car trouble. He claims Garcia’s severed head as his trophy after dispatching the men. Stopping at a roadside establishment, he uses ice to preserve the head for transportation, eerily conversing with it as though it were alive, expressing a blend of anger and admiration over Elita's death.
Just then, Bennie is ambushed by Garcia's relatives, who reclaim the head and prepare to execute him. Their violent confrontation is halted by the sudden appearance of Sappensly and Quill. The hitmen execute most of Garcia's family members in a barrage of gunfire, with Quill succumbing to a bullet wound. As Sappensly mournfully gazes at Quill's lifeless body, Bennie quips, "Do I get paid?" and, in a swift turn of fate, kills Sappensly.
Returning to Mexico City, Bennie engages in a surreal dialogue with Garcia’s head along the way. Once in his apartment, he cleans the head and takes it to Max’s hotel room. When he feigns his readiness to hand over the head for the bounty, it becomes evident that his motives have shifted; he reveals his deep-rooted frustrations over the chaos surrounding Garcia's demise and blames it for Elita’s tragic fate.
In a fit of rage, Bennie confronts Max and his henchmen, leading to a violent showdown that culminates in Bennie claiming El Jefe’s address from Max’s desk. After attending the baptism of El Jefe's grandchild, Bennie is welcomed as a hero in El Jefe's estate, receiving the coveted million-dollar bounty. However, he chillingly recounts all the lives lost for Garcia's head, leading to mounting tension as El Jefe dismisses the head as mere swill for pigs.
As Teresa, with her newborn, enters the scene, Bennie's resolve wavers. She urges him to finish the job and eliminate her father. With a reluctant acceptance, Bennie obeys, leaving El Jefe's estate with Teresa and Garcia's head. Just as they reach the exit, Bennie softens, instructing Teresa to care for her son, adding, "And I'll take care of the father." Tragically, as he drives away, El Jefe’s men ambush him, mercilessly turning him into a target, their machine guns ripping him apart.
