As the relentless sun scorches the dusty streets of a small Mexican town, Azul, a fierce criminal with a knack for violence, breaks free from his confines in the local jail. He bursts forth with a guitar case packed not with music, but with an arsenal of weapons, driven by one singular aim: to unleash chaos upon Moco, the formidable drug lord who orchestrated his imprisonment.
Simultaneously, a young musician, known as the Mariachi, steps off a bus, clutching a well-worn guitar case that symbolizes not just his passion for music, but his dreams of becoming a mariachi like his father. However, he's unaware that danger lurks in every corner of this town. Moco, the brain behind the area's cartel, has sent his skilled Sicarios to hunt down Azul and terminate his reign of terror. The streets now turn into a battleground, as these ruthless operatives seek their prey, a man in black wielding a guitar case.
In a twist of fate, the Mariachi finds himself inadvertently ensnared in this violent conflict. As Moco's henchmen close in, the Mariachi is compelled to defend himself. Armed only with his guitar, he fends off four attackers, showcasing his resourcefulness and resilience. Seeking refuge, he stumbles into Dominó's bar, instantly captivated by the allure of its beautiful owner. Unfortunately, it soon becomes clear that her ambitions lie with Moco's wealth, pulling her deeper into the drug lord's treacherous game.
A pivotal moment occurs when Azul, also holding a guitar case, unknowingly swaps it with the Mariachi's instrument. As chaos ensues, Moco's men mistakenly capture Azul in a wild pursuit, releasing him only when they realize their blunder. Meanwhile, the Mariachi is captured and presented to Moco, who dismissively declares, > "You're not Azul." Fortunately, the Mariachi is set free, the guitar case still firmly grasped in his hands.
Now adrift in a perilous world dictated by Moco's whims, the Mariachi asserts control over Dominó, coercing her to lead him to Moco's stronghold under threat of dire consequences. Driven by a protective instinct for the Mariachi, Dominó reluctantly agrees.
Upon reaching Moco's heavily guarded compound, the Mariachi concocts a plan, pretending to take Dominó hostage to gain access. Yet, Moco's sharp intuition quickly unveils the charade. Angered by what he perceives to be Dominó's betrayal, Moco unleashes a torrent of bullets that claim both the Mariachi and Dominó, casting their fates into turmoil.
As the Mariachi regains consciousness amidst the wreckage of shattered dreams, he discovers the lifeless body of Dominó beside him. Crippled from Moco’s merciless attack, the loss ignites an inferno of vengeance within him. Gripped by sorrow and rage, he seizes Azul's abandoned weapon in pursuit of retribution against Moco.
With the cowardly henchmen abandoning their leader in the face of his tyranny, the Mariachi mournfully eyes the aftermath of his wrath. As daylight fades into darkness, he rides away on Dominó's motorcycle, accompanied by her loyal pit bull and a poignant keepsake—her letter opener. The dreams of a mariachi life now lie in ruins, as he clutches the cold steel of Azul's discarded arms, forever binding him to Dominó's memory.
