Bounty hunter Jack Walsh is enlisted by bail bondsman Eddie Moscone to bring accountant Jonathan “The Duke” Mardukas back to Los Angeles. The accountant had embezzled $15 million from Chicago mob boss Jimmy Serrano before skipping on the $450,000 bail Moscone had posted for him. Walsh must bring Mardukas back within five days, or Moscone defaults. Moscone says the job is easy, a “midnight run,” but Walsh demands $100,000. Walsh is then approached by FBI Agent Alonzo Mosely, who wants Mardukas to be a witness against Serrano and orders Walsh to keep away from Mardukas. Walsh takes no notice of this and instead steals Mosely’s ID, which he uses to pass himself off as an FBI agent along his journey. Serrano’s henchmen Tony and Joey offer Walsh $1 million to turn Mardukas over to them, but he turns them down.
Walsh captures Mardukas in New York City and calls Moscone from the airport, not knowing that Moscone’s line is tapped by the FBI and that his assistant Jerry is secretly tipping off Serrano’s men. However, Mardukas fakes a panic attack on the plane, forcing the two men to travel via train. When Walsh and Mardukas fail to show up in Los Angeles on time, Moscone brings in rival bounty hunter Marvin Dorfler to find them. Dorfler tracks them to the train and attempts to take The Duke from Walsh, but Walsh gets the drop on him and leaves the train. However, he discovers when he attempts to purchase bus tickets with a credit card that Dorfler canceled the card.
Without funds, he is forced to rely on other means to get across the country, including stealing cars, borrowing his ex-wife’s car in Chicago, and hitchhiking. Meanwhile, word of the skirmish on the train reaches Mosely’s ears and he leads a task force to find Walsh and Mardukas.
Walsh eventually reveals that, 10 years before, he was an undercover officer in Chicago trying to get close to a drug dealer who had almost the entire police force on his payroll. Eventually, just as Jack was going to bust the dealer, he had heroin planted in his house by corrupt cops. In order to avoid either going to prison or working for the dealer, Walsh resigned from the force, left Chicago and became a bounty hunter, while his wife divorced him and married a corrupt lieutenant. Since then, however, Walsh has clung to the vain hope that he will one day be reunited with his ex-wife. Later, Mardukas learns that the drug dealer was Serrano, with Walsh not caring about the likelihood of Mardukas getting murdered by the man who ruined Walsh’s life.
In Arizona, Dorfler takes Mardukas away from Walsh, who is later found by Mosely and arrested. In Mosley’s custody, Walsh is allowed his right to make phone calls and while arguing with Moscone over the phone, Walsh realizes that Dorfler intends to turn Mardukas over to Serrano for $2 million. However, Dorfler accidentally reveals to Serrano’s men where he is keeping Mardukas and is knocked unconscious by Serrano’s men, who go after Mardukas themselves.
Walsh calls Serrano’s men and bluffs that he has computer disks created by Mardukas with enough information to put Serrano away, but promises to hand the disks over if Serrano returns Mardukas to him unharmed. Jack arranges a deal with Mosely to frame Serrano in turn for his release and to allow him to deliver Mardukas to Moscone. He meets up with Serrano while wearing a wire and being watched by the FBI. Dorfler spots Mardukas and interrupts the exchange, unknowingly disabling the wire. After Serrano takes the disks, the FBI closes in, arresting Serrano and his henchmen.
Mosely turns Mardukas over to Walsh with enough time to return him to Los Angeles before midnight. However, Walsh calls Moscone to confirm he’s made the deadline, then promptly lets Mardukas go. Before parting, Walsh gives Mardukas the watch his wife gave him before their marriage. In return, Mardukas gives Walsh $300,000 in a money belt he had been hiding, insisting that it is a ‘gift’ not a payoff–since Walsh had already chosen to let him go. Walsh accepts and flags down a taxi, asking the driver if he has change for a $1,000 bill, but the taxi drives away, so he heads home on foot.