Abby, the wife of bar owner, Julian Marty, begins an affair with Ray, one of Marty's bartenders. Driving through a rainstorm at night, unaware of a Volkswagen Bug following close behind them, Ray gives Abby a ride to Houston, Texas, as she attempts to separate from Marty. Despite their uncertainty, the expedition is curtailed when they consummate the relationship at a motel. In the morning, a man calls the room and, after hanging up, Ray tells Abby that it was her husband. Already suspicious, Marty hired private detective, Loren Visser, to investigate, and Visser confirms Marty’s fears with photographs of Ray and Abby at the motel. When Marty angrily demands to know why he took the pictures even though he had already called to let him know that they were together, Visser wields a silver lighter engraved with his name and claims that voyeurism is one of the perks of the job. Marty threateningly tells Visser that in Greece it is customary to cut off the head of a messenger who brings bad news, but Visser laughs and leaves with his payment. The next evening, Ray takes Abby back to her house, where she secretly collects the pearl-handled revolver Marty gave her as a gift, and he offers to let her stay at his place. He then goes to Marty’s bar to quit and claim unpaid wages. Marty refuses to pay and warns Ray that Abby will cheat on him as well. Marty’s comment elicits mistrust, and although a quarrel ensues between Ray and Abby when Ray returns home, they spend the night together. In the morning, Marty hides in Ray’s living room and attacks Abby, who unsuccessfully reaches for the revolver in her purse. The fight continues outside, where Abby kicks Marty in the groin, and when Ray appears at the door with Abby’s gun, Marty retreats. Later, Marty meets Visser, who has parked his Volkswagen Bug at a popular teen hangout, and offers him $10,000 to kill Ray and Abby. Reluctant at first, Visser accepts and tells Marty to arrange a fishing trip as an alibi. That night, Visser breaks into Ray's house, steals Abby's gun and then returns outside to stalk the couple through the large, exposed window beside Ray’s bed. Marty returns from his trip and meets Visser at the bar office. Visser presents him with a photograph displaying Ray and Abby in bed, shot and killed. When Marty opens the safe to withdraw Visser’s fee, he hides the photograph inside. After Visser collects his money, he shoots Marty with Abby's gun, but accidently leaves his lighter under a dead fish on Marty's desk. Later that night, Ray returns to the bar, seeking the wages he is owed. Not finding anything in the cash register, he walks into the office, stumbles over Abby’s revolver, which misfires, and finds Marty in his chair, covered with blood. Assuming Abby shot Marty, Ray attempts to clean up the office with his windbreaker, then slips her gun into Marty’s pocket and drags the body to his car. After driving away, Ray pulls over and runs from the car, but turns back to find that Marty is no longer in the backseat. As Marty slowly crawls away, Ray considers running him over with the car and beating him with a shovel, but cannot muster the will. He drags Marty back into the car and drives to a freshly plowed field. After digging a hole, Ray buries Marty alive. Before he is completely covered, however, Marty weakly draws Abby’s revolver from his pocket. He points it at Ray and squeezes the trigger, but there are no remaining bullets. Now panicked, Ray frantically finishes filling the grave with dirt. In the morning, Ray calls Abby from a payphone and tells her that he loves her, then shows up at her new apartment with blood on his shirt. Meanwhile, in a darkroom, Visser sets fire to the photographs he doctored to show the murder of Abby and Ray, but realizes the one Marty returned to him has been replaced with a sign from the bar reminding employees to wash their hands before returning to work. He attempts to light a cigarette and discovers his lighter is missing, then taps his fingers on his phone. Back at Abby’s apartment, Ray vaguely describes the events from the previous evening and how he cleaned up her mess, but Abby does not understand what he is talking about. They are interrupted by a phone call, but when Abby picks up, she hears nothing on the other end and assumes that it is Marty. Still unconvinced that Abby did not attempt to kill Marty, Ray leaves, but sets Abby’s gun down by the door on his way out, telling her that she had left it behind. That evening, in an attempt to make sense of Ray's behavior, Abby goes to the bar. When she arrives, Visser is in the office, trying to break open the safe with a hammer to reclaim the incriminating photograph. Visser hides and watches as Abby uncovers broken glass and blood on the floor, a hammer and chip marks on the safe, and fish rotting on Marty’s desk. Suddenly back at her apartment, Abby wakes in the night and washes her face. Hearing footsteps through the walls, Abby leaves the bathroom to find Marty sitting on her bed. He says that he loves her and that she left her weapon behind, tossing a threatening metal object from his pocket that turns about to be a compact. With the warning "he'll kill you too," Marty falls on the ground, vomiting blood. Abby wakes from the apparent nightmare and sits up in bed. She goes to Ray's apartment and accuses him of murdering Marty over the money he is owed, but Ray, who is packing to leave, explains that he found her gun at the bar and buried Marty alive. A newspaper loudly strikes the screen door beside them, and Abby leaves in haste. Ray returns to the bar and finds Visser’s doctored photograph. Upon leaving, he notices a Volkswagen Bug on the empty street. That night, Abby returns to her apartment to discover Ray waiting in the dark, looking out the window. As she switches on the lights, he urges her to turn them off. She does, but when he explains that he thinks someone is watching, she turns the lights back on in fear that he plans to hurt her. Visser, watching from the rooftop of a building across the street with a sniper rifle, uses the light to aim and fires a shot through the window. Ray falls down dead and Visser targets Abby, who dives to the floor and narrowly avoids the bullet meant for her. Barely out of Visser's view, she throws a shoe and shatters the light bulb, plunging the room into darkness. Visser soon arrives at the apartment and Abby hides in the bathroom. He searches Ray in an attempt to retrieve his lighter but does not find it, then moves on to the bathroom to kill Abby. When he does not see her there, he reaches out the bathroom window toward the building’s adjacent window. As he slides it open, Abby grabs him, slams the window frame down on his wrist and stabs his hand with a knife. The blade goes deep into the windowsill, immobilizing Visser. Desperate, he shoots holes into the wall, and, when his gun is empty, he breaks through the wall with his fist. Abby returns next door to her apartment and finds her gun where Ray left it while Visser removes the knife from his hand. Aiming her gun from outside the partially closed bathroom door, Abby sees Visser’s shadow, fires a shot and hits him. As he falls to the ground and hears Abby declare, "I'm not afraid of you, Marty," Visser bursts into laughter. With his last breath, Visser jokes that if he sees Marty, he’ll “give him the message” and looks up at the underside of the bathroom sink. Water collects on the pipes and a single drop falls on him.