In a dark and filthy kitchen, an unkempt man dons surgical gloves and swiftly downs a glass of cheap whiskey. Lying face down on the kitchen table is Porter, portrayed by Mel Gibson, who is gravely injured with two sizeable bullet wounds in his back. The doctor, in a desperate attempt to save him, pours whiskey on Porter's wounds for sterilization before extracting the bullets. After spending five long months recovering, Porter reflects on the $70,000 that was stolen from him — a sum he is determined to reclaim.
With no money to his name, Porter exits the subway and shamelessly swipes cash from a 'blind' homeless man's donation hat. When the homeless man protests, Porter retorts with a cold, “Shut up, I cured you.” He then scans the bustling sidewalk, identifying a man who resembles him but is better off. Bumping into this target, he deftly lifts the man's wallet. The afternoon unfolds with Porter indulging in a shopping spree, purchasing fine clothes, withdrawing cash from a bank, and acquiring jewelry to pawn for $500 and a handgun. However, his extravagant spending comes to an abrupt halt when a restaurant waiter informs him that his credit card was declined. Without skipping a beat, Porter instructs the waiter to try again before darting out without paying his bill.
Now on a quest, Porter begins tracking down Val Resnick (played by Gregg Henry), his former partner, and Lynn (portrayed by Deborah Unger), his estranged wife, who has succumbed to heroin addiction. Both treacherously abandoned him following a $140,000 heist from the Chinese triads, after which Lynn shot Porter and left him for dead. Resnick, opting for safety, aligned himself with the Outfit, a powerful crime syndicate, and used a sizable portion of the stolen funds to settle his own debts. Fueled by anger and a thirst for revenge, Porter is determined to reclaim his $70,000 share.
To achieve this, Porter recruits the help of a call girl, Rosie (played by Maria Bello), who is linked to the Outfit. Their relationship is steeped in history; Porter once served as her driver, which led to a brief encounter, further complicating their dynamics. Lynn's jealousy and Porter's infidelity with Rosie led to their betrayal. To navigate this dangerous terrain and reach Resnick, Porter must face a slew of adversaries, including a lowlife named Arthur Stegman (David Paymer), as well as crime lords from the Outfit, the Chinese triads, and corrupt detectives Hicks and Leary (Bill Duke and Jack Conley).
Porter's confrontation with Resnick is chaotic and violent; Resnick is with a dominatrix, (Lucy Liu), when Porter crashes back into his existence. Attempting to explain the situation to the Outfit, Resnick is compelled to take matters into his own hands but winds up shot by Porter in Rosie's apartment when he finds Resnick mistreating her while Porter had merely returned to pick up his forgotten cigarettes.
The tension escalates as Porter efficiently dispatches three members of the Outfit's hit squad, including their commander, Philip (John Glover), who were dispatched by Carter (William Devane) to deal with Porter. Porter, filled with fury, threatens Carter with death next if the higher-ups don’t settle his debt. When mob boss Bronson (Kris Kristofferson) refuses to pay, Porter takes drastic measures.
With Rosie's assistance, Porter kidnaps Bronson's son Johnny, keeping him restrained. He cleverly orchestrates a plan to expose Hicks and Leary by planting Leary's fingerprints on the weapon he used to kill Resnick, later discarding Hicks's badge with the gun near Resnick's body.
As Bronson and his accomplice, Fairfax (James Coburn), close in on Porter, the situation spirals out of control, culminating in his capture by the Outfit amid a chaotic sequence involving the triads. In a brutal turn of events, Porter endures torture at the hands of his captors, with his toes smashed mercilessly.
Ultimately, Porter is confined in the trunk of a car and transported to an apartment rigged with explosives. After a series of explosive events lead to the demise of his captors, he is rescued by Rosie, who has come to support him along with her dog, also named Porter. When she inquires about his injuries, Porter quips, > "I got hammered." Together, they drive off towards Canada, ready to start anew.
