Thirty years after a devastating nuclear apocalypse, Eli (Denzel Washington) embarks on a perilous journey on foot towards the west coast of the United States. As he navigates the harsh landscape, he utilizes his exceptional survival and combat skills, deftly hunting wildlife and thwarting an ambush set by a group of highway bandits.
In his quest for water, Eli stumbles upon a dilapidated town controlled by Carnegie (played by Gary Oldman), a powerful man with grand aspirations of establishing more towns through manipulation, wielding the influence of a specific book. His men scour the wasteland daily, desperate to find it, but their efforts yield no results.
While at the town bar, Eli encounters and eliminates a band of bikers who threaten him. Recognizing Eli as a literate individual, Carnegie coerces him into staying, asserting that the offer is non-negotiable. After receiving food and water from Carnegie's blind concubine Claudia (Jennifer Beals), he sends her daughter Solara (Mila Kunis) to entice Eli. However, Eli rejects her advances, but not before she discovers the book he possesses. Eli reassures Solara with a firm yet compassionate approach, inviting her to pray with him before sharing his meal.
The next day, Solara prays alongside her mother, and unaware of Carnegie's eavesdropping, they affirm Eli's literacy. Realizing the potential connection to the book he seeks, Carnegie resorts to violence to extract information from Solara, who inadvertently shares that Eli is in possession of a Bible. Undeterred, Eli sneaks out to meet the Engineer (Tom Waits), who he had previously asked to recharge his music player battery.
In an attempt to capture Eli, Carnegie orders his henchmen to fire upon him, but miraculously, the bullets barely touch him as if guided by fate. Eli retaliates, taking down several henchmen and wounding Carnegie in the leg. After Eli escapes, Solara follows him, leading him to the town's water source, where she hopes to accompany him on his journey. Eli, however, chooses to leave her behind for her safety.
Yet Solara is soon caught by bandits with malicious intentions, only for Eli to appear and defend her. As they travel together, Eli reveals that the Bible he carries is the last intact copy, destroyed by authorities after the war, and that he has been directed by a divine voice on this quest for the last thirty years, ensuring his protection.
Their journey brings them to the eerie residence of Martha (Frances de la Tour) and George (Michael Gambon). Initially welcomed, they soon discover the couple's sinister intentions, finding themselves trapped in a desperate struggle for survival as Carnegie and his men close in. In a violent confrontation, Eli and Solara fight back, leading to the deaths of both their hosts and Carnegie's men. Cornered, Eli ultimately surrenders the Bible to save Solara when Carnegie threatens her life.
As fate would have it, Solara escapes and returns to rescue Eli. Instead of pursuing her, Carnegie decides to return to town with the Bible, facing dwindling resources. Solara picks Eli up, and together they journey westward until they reach the iconic Golden Gate Bridge, where they row to Alcatraz. There, they meet a community of survivors. Eli informs the guards of his possession of the King James version of the Bible, granting them entrance.
Inside, Eli is introduced to Lombardi (Malcolm McDowell, uncredited), the curator, and it’s revealed that Eli is blind as he begins to dictate the Bible from memory. Meanwhile, Carnegie, back in town, manages to access the Bible, only to find it written in Braille. His frustration grows as he realizes that his obsession with Eli has led to his own downfall. With his leg wound becoming infected, he confronts a grim reality as chaos erupts in his town, ultimately losing control.
As Eli completes the dictation of the Bible, he succumbs to his injuries and passes away. The Alcatraz printing press begins producing the new King James Bible, placing it on shelves beside the Torah and the Qur'an. Although Solara is offered refuge within the sanctuary of Alcatraz, she opts to return home, taking with her the belongings that once belonged to Eli, honoring his memory and legacy.
