One night in Detroit, Michigan, Frank Stringer of the Auto Workers Alliance (AWA) and his secretary, Liz, are murdered by a gang called the Invisible Men: Gamble, Thaw, Shaker, Marlin, and Birch. The following day Albert, a purse thief, is arrested and brought to the police station. The officers warn him of the temperamental Harvard Law School graduate Sergeant Jericho “Action” Jackson. Albert attempts to escape, but spills coffee on Jackson’s desk, and when Jackson speaks to him, Albert faints. After, Jackson meets with Capt. Armbruster, who orders him to attend the Detroit Businessmen League’s Man of the Year Fundraiser, honoring Peter Dellaplane, a prominent automobile maker. Upset, Jackson argues that Dellaplane provoked his demotion to sergeant from lieutenant. That evening at the fundraiser, Jackson meets Patrice, Dellaplane’s second wife, as Dellaplane gives a speech. Elsewhere, the Invisible Men blow up a yacht, killing all onboard, including Lionel Grantham, an official at AWA. Jackson returns home after the fundraiser, listens to a telephone message from his friend, Tony Moretti, and watches a television report about the explosion. The next day Tony telephones the station, looking for Jackson. Jackson goes to Tony’s apartment and sees Tony holding a gun. Tony fears that he himself will be killed because he knows Dellaplane is ordering the murders of AWA officials. Tony advises Jackson to talk to Sydney Ash, who is a singer at Joey’s Club Elite, and Dellaplane’s mistress. After Jackson leaves, an Invisible Men gang member kills Tony. Meanwhile, at the club, Dellaplane watches Sydney rehearse a song. When she finishes, they go to her apartment and Dellaplane gives her a syringe for her drug habit. Later, Jackson learns from the coroner that Tony is dead and Jackson’s former partner, Detective Kotterwell, rules the death a suicide. However, Jackson is convinced that Tony was murdered. The following day, Dellaplane and Patrice entertain AWA president Raymond Foss at an exclusive restaurant. Jackson arrives unexpectedly to inform Dellaplane of Tony’s death, but the tycoon replies that he doesn’t know Jackson’s deceased friend. Later, at Dellaplane’s mansion, Patrice leaves the steam room and overhears Cartier, one of Dellaplane’s henchmen, on the telephone mentioning Tony and what the deceased man might have told Jackson. Patrice tries to discuss the matter with Dellaplane, but he leaves for a meeting. After dressing, Patrice opens the front door to find Jackson, and they drive into town together. At a bar, Patrice tells Jackson what she overheard about Tony and a man named Oliver O’Ronney. When they leave, an Invisible Man, Gamble, attempts to run them over with a taxi. Jackson pulls Patrice out of the way, and chases the taxi on foot, as Gamble tries to ram into Jackson with the vehicle. Although Jackson jumps over the taxi before it crashes into a building, Gamble escapes. Returning to the police station, Jackson looks for Patrice and an officer gives him a note from her, stating her intention to tell Dellaplane what she overheard about Tony. That night Jackson talks to Sydney at the club. He goes backstage, but is stopped by Sydney’s bodyguard, Edd. After shoving Edd through the dressing room door, Jackson leaves with Sydney. Meanwhile, Dellaplane returns home and Cartier hands him a recently cleaned gun. He finds Patrice crying in the bedroom and she tells him about Cartier’s telephone call. When she mentions she spoke to Jackson, he shoots her dead with his gun. While driving with Sydney, Jackson sees police cars in front of his building. He learns from his car’s police radio that Patrice has been murdered and her body was found in his apartment. They drive to Sydney’s apartment, arriving as the telephone rings and triggers an explosion. The two escape and hide in a hotel. There, Jackson introduces Sydney to Kid Sable, the hotel clerk and a former prizefighter. The next morning, Jackson and Sydney find his car stripped, then walk to a local poolroom to look for a former informant of Jackson’s. However, the bartender leads him to the backroom and knocks him unconscious. When Jackson awakens, a trio of criminals and the bartender announce their plan to castrate him. Sydney arrives, claiming that Jackson is her mentally unstable brother. He acts along with Sydney’s lie, then fights the group and Jackson and Sydney escape to the hotel. Kid Sable directs Jackson to a barbershop stylist named Dee and while Sydney stays in the hotel room, Jackson learns about the Invisible Men from Dee. She also informs Jackson that Oliver O’Ronney is in the AWA and frequents a bar called the Red Devil. Returning to the hotel room, Jackson finds Sydney missing, but locates her in another room with Mr. Quick, a drug dealer. As Jackson fights Mr. Quick and throws him through the window, two police officers witness the scene. Jackson and Sydney leap from the window onto Jackson’s car and steal the police car. While driving, Jackson tells Sydney how Dellaplane framed him for Patrice’s murder. Warning that she will be Dellaplane’s next victim, he convinces her to help him. Later that night, they drive to the Red Devil, and Sydney kisses Jackson before heading inside. There, she finds O’Ronney and tells him Dellaplane sent her. As they leave the bar, Edd watches unnoticed. Early the next morning, Sydney and O’Ronney drive to an empty factory to supposedly meet Dellaplane, but Jackson is there instead and asks O’Ronney about Dellaplane’s plan. O’Ronney informs Jackson that Dellaplane is going to kill AWA president Raymond Foss at a party that night and blame the murder on Jackson. Suddenly, Sydney yells for help and Jackson finds she is being held hostage by the Invisible Men. He too, is captured and brought to another factory, where Dellaplane tells him he wants control of the AWA and that he murdered Patrice. He then explains that Gamble will kill Foss, disguised as Jackson. Dellaplane leaves, ordering three Invisible Men to kill Jackson. However, Sydney’s bodyguard, Edd, rescues Jackson. That evening, Dellaplane hosts an outdoor party for Foss. Jackson sneaks in and sees Gamble in a tree with a sniper rifle, aimed at Foss. After creating a distraction, Jackson knocks Gamble out of the tree and onto metal fence posts, where he is fatally impaled. Meanwhile, Dellaplane holds Sydney hostage. As party guests panic and run, Sydney screams for Jackson from the mansion’s second story. He drives a car inside the mansion and maneuvers the vehicle upstairs, crashing into the room. As Jackson fights his nemesis, Dellaplane fires his gun, hitting Jackson’s shoulder. However, Jackson grabs a gun at the same time and shoots Dellaplane dead. Sometime later, police Capt. Armbruster assesses the crime scene and promotes Jackson to his former rank of lieutenant. Sydney promises Jackson that she will stop using drugs and they kiss.