Professional assassin Vincent arrives at Los Angeles International Airport, where an anonymous contact passes him a laptop computer with detailed information on the individual locations of five victims to be murdered that night. Simultaneously, cab driver Max Durocher meticulously tidies his taxi before beginning his daily shift. At dusk, Max picks up Annie Farrell, a prosecuting attorney returning to her office in preparation for an important upcoming trial. During the ride, Annie is impressed by Max’s sharp observations and shrewd assessment of her and confides a little about the tensions of her work. Max reveals his plans to start his own private limousine company to be called Island Limos. Upon arriving downtown, Annie offers Max her business card and as she enters the court building, Vincent exits it and hails Max’s cab. After settling into the car, the impeccably dressed Vincent gives Max his destination address, notes the car’s cleanliness and mentions his distaste for the cold anonymity of Los Angeles, where a man can die on the subway and no one notices. Arriving at the address, Vincent reveals that he is closing a critical real estate deal and needs several signatures all over town before catching an early morning flight, then offers to hire Max all night for six hundred dollars. Although it is against his company’s policy, Max reluctantly agrees. Unable to double-park on the main street, Max drives to a back alley to wait for Vincent and moments later is stunned when a body crashes onto the cab’s roof from a floor above. Bolting from the car, Max surveys the body in horror, and when Vincent returns, realizes by his detached demeanor that he is the killer. When Max demands to know why Vincent killed the man, Vincent coolly points out that he only shot him, the bullets and the fall killed him, then orders the shocked Max to help him place the body in the trunk. Astonished, Max refuses until Vincent pulls a gun on him. After Max and Vincent place the dead man in the trunk and return to the cab, Vincent asks Max why he should care about the death of a stranger and assures him the victim was a criminal. As they proceed to the next address that is listed in Vincent’s laptop, the cab is stopped by the police, who inquire about the cracked windshield and dented roof. Terrified that Vincent will kill the officers, Max claims to have hit a deer, but as the police order the men from the car, their dispatcher issues an immediate summons to a crime in progress. At the next location, Vincent apologetically ties Max’s hands to the steering wheel, and as Vincent is about to leave, Max’s dispatcher radios to ask about the police report on the damaged cab. When Max fumbles for an explanation, Vincent abruptly grabs the radio and tells the dispatcher he is a lawyer, bullying him into silence. After Vincent enters the building in search of his next victim, Max struggles to untie his hands and in frustration honks the horn and flashes the car lights, which draws a passing gang. Several men approach the car and a grateful Max pleads for them to untie him, only to have one man pull a gun and demand his wallet. Spotting Vincent’s briefcase, which contains the laptop, in the back seat, the man takes it and he and his partner walk away only to be confronted by Vincent. The men scoff at Vincent’s demand to return his briefcase and, as Max watches in dismay, Vincent shoots both men and retrieves his bag. Returning to untie Max, Vincent reproaches him for causing unnecessary deaths by drawing attention to himself. To Max’s bewilderment, Vincent declares that as they are ahead of schedule they should visit a jazz club. Meanwhile, undercover narcotics detective Ray Fanning discovers that informant Ramon Aiella, Vincent’s first victim, has disappeared and summons his chief, Richard Weidner, to Aiella’s apartment. Dismissing Fanning’s suggestion that Aiella has been murdered, Weidner reconsiders when a bullet casing is found in the apartment. Across town at a jazz club, Vincent listens with appreciation to a jam session, then invites the horn soloist and club owner, Daniel Baker, to join him and Max for a drink. Vincent listens enthusiastically as Baker rhapsodizes about jazz, but when Vincent makes a reference to drugs, Baker falls silent. Realizing Vincent's mission, Baker sends apologies to the drug lord for whom he once worked, acknowledging that he turned state’s evidence against him in order to avoid returning to prison. Vincent then shoots Baker point blank in the head. Dazed, Max stumbles from the club, insisting he cannot continue. Vincent throttles Max against the cab, but is interrupted by the dispatcher’s angry call asking Max to contact his mother. Startled, Vincent presses Max for an explanation and the driver reveals he visits his hospitalized mother every night. Insisting Max cannot break routine and draw attention to himself, Vincent forces him to drive to the hospital to see his mother Ida. Vincent accompanies Max, but when the hit man charmingly engages Ida, the disgusted Max abruptly snatches Vincent’s briefcase and races from the hospital. Vincent follows but is unable to prevent Max from flinging the briefcase onto freeway traffic. Meanwhile, Fanning visits the hospital mortuary to examine three new bodies. The medical examiner points out that although two of the men were brought in separately, they were all murdered and have identical bullet wounds. Upon examining the body of Vincent’s second victim, Fanning recognizes crooked lawyer Sylvester Clarke, and immediately contacts Weidner, as both Aiella and Clarke were informants in their investigation of drug lord Felix Reyes Torina. Just outside the hospital, Vincent forces Max back to the cab and orders him to drive to another nightclub, El Rodeo, where the assassin directs Max to impersonate Vincent and meet with Felix in order to recover the information about his final two victims that was on the laptop. Although terrified, Max complies, unaware that the club is staked out by the FBI, who are also investigating Felix. Posing as Vincent, Max gains an audience with Felix, who is dumbfounded when “Vincent” reveals he has lost the detailed hit information. During their conversation, Fanning and Weidner join the federal agents, led by Frank Pedrosa, to warn him about Aiella and Clarke’s deaths and the just reported murder of Baker. Stunned, Pedrosa reveals that all three men were federal witnesses in their case against Felix. Using the security monitors surrounding the club, the agents see and hear Max identify himself as “Vincent,” and Fanning spots the damaged cab sitting in the alley. Checking the license number, Fanning learns from the cab company that Max is law-abiding and has driven for a dozen years without incident, but Weidner insists "Vincent" is the hitman. Inside El Rodeo, Max abruptly overcomes his nervousness and demands the information needed to complete his job and Felix grudgingly complies, giving him a computer memory key. Back at the cab, Vincent plugs the computer memory key into the cab’s mobile data terminal and orders Max to drive to a Koreatown club, Fever. Meanwhile, Pedrosa has his men follow the cab while Fanning reminds Weidner of a suspicious case years earlier where a cab driver inexplicably committed several murders before killing himself. Fanning suggests that Max is a “front” for the real murderer, but Weidner, content to let the federal agents take over, departs. At Fever, Vincent forces Max to accompany him into the crowded, pulsating club in search of his next victim, Peter Lim, unaware that the federal agents are close behind, and believe that Max is the assassin. As the men push through the crowd and the agents also move in, Lim’s private guards panic and begin shooting. In the ensuing melee, Pedrosa is wounded, several of the agents are killed and Vincent unexpectedly saves Max from being shot by a guard. As the club crowd flees in panic and the agents continue focusing on Max, Vincent reaches Lim and kills him. Meanwhile, Fanning, who has followed the agents to the club, grabs Max to rescue him. As they get outside, however, they find Vincent already back at the cab, where he shoots Fanning and orders Max to resume driving. Outraged by the depth of Vincent's callousness, Max furiously races through the streets and, when Vincent berates Max for being a weak failure, purposely crashes the cab. Both men survive, but as police sirens wail nearby, Vincent flees. A policeman arrives and offers to help Max until he spots Aiella’s body in the trunk. As the policeman is about to handcuff Max, the cabbie spots the picture and information of Vincent’s last victim on the monitor and is stunned to recognize Annie. Galvanized, Max overpowers the policeman and, taking a pistol, races toward the court building several blocks away. On the way, Max steals a cellphone from a pedestrian and, reading the number on Annie’s business card, phones her. Although confused and startled when Max babbles about the killings and Vincent, when he mentions Felix, Annie realizes she is in danger. Meanwhile, Vincent arrives at the court building, kills the security guards and makes his way to Annie’s top floor office, not realizing she is in the library two floors below. Frustrated when the cellphone battery abruptly dies, Max hastens to the building and confronts Vincent just as the killer finds Annie in the library. Max wounds Vincent, then flees with Annie down to the subway. Vincent revives and follows the couple onto a mostly empty subway train, chasing them into the last car, where the men have a violent shootout in which Max survives, but Vincent is fatally wounded. As he slumps down on a seat before dying, Vincent asks Max if anyone would notice a dead man on the subway. As dawn breaks, Max and Annie get off at the next stop together.