A woman is driving home at night and listening to a radio report about a recent series of hit-and-run attacks. As she continues driving, the radio stutters and dies, and a black Impala rams her off the road and down the side of the mountain.
As Dean and Sam are driving through the town a few days later, Sam admits that he hasn't found any recent cases that involve the supernatural. He also hasn't turned up anything on their father's whereabouts. A police car pulls the brothers over and the officers immediately arrest them and take them to the station. The chief of police, Rod, interrogates them but doesn't believe their claims that they're innocent because a black Impala matching their car's description has been responsible for a series of deaths in the area. He throws the brothers in jail and Sam figures that they can prove their innocence, but Dean doesn't want to wait.
The deputy chief of police, Michael, comes onto the officer standing watch and steals the cell keys. He then goes to the cell and lets the Winchesters out. He introduces himself and explains that he's Rod's brother, and apologizes for the police chief's behavior. Michael explains that they lost their parents when they were young and Rod has never gotten over it. As the brothers prepare to leave, Sam wonders why Michael is helping them and he blurts out that the killer may not even be human anymore. When the brothers push for more details, Michael tells them that he was just joking. He says that he just helped them escape because they're his type and because they were innocent, and then wishes them well.
When Michael goes home, he finds Rod waiting for him. The police chief knows that the Winchesters have escaped and figures that Michael is responsible. Michael says that they both know the Winchesters are innocent and accuses Rod of blaming the brothers to avoid his own guilt. Rod asks if Michael told them about it and his brother says that he didn't, and wonders how Rod could think he would betray him.
As Sam and Dean drive out of town, they wonder what Michael meant about the killer not being human. Sam doesn't want to let it go and Dean reluctantly turns the Impala around and prepares to head back. He insists that he has his own reasons for going back and wonders how they can get the Impala in, and Sam tells him that he has a plan. They paint the Impala white with a water-based paint and Sam emails Michael and arranges a meeting at a diner. When they get there, the brothers start to explain that they're hunters but Rod and his men come in for coffee. Rod recognizes the Impala despite the paint job but discovers that Michael and the Winchesters have slipped out the back.
Michael drives the brothers away in his police car and they tell him that they hunt monster. He finally agrees to tell them the truth and explains that two summers ago, a bank robber in a black Impala was heading toward town. Rod and his men set up a roadblock, but the robber kept driving and was killed in a car crash. However, later Rod learned that the real robber was caught elsewhere and that the man they drove to his death was an innocent man who panicked. The police covered up the incident and everyone in town went along with it. Since then, the ghost Impala has gone after the town's residents, killing them off. The Winchesters tells Michael that they can handle it and have him take them to the site of the car crash two years ago.
As they drive, Sam and Dean explain that they have to salt and burn the ghost's bones. Dean is eager to get to the Impala but Sam and Michael both warn him that it's too risky. As Sam and Dean start fighting in the back, Michael admits that he and his brother still fight but that they love each other no matter what. Rod pulls them over and knocks Michael to the ground with a shotgun. He refuses to listen when Michael says that the Winchesters can help them, and tells the brothers to get out of the car. As they do so, Michael grabs the gun and knocks Rod down. However, the ghost Impala pulls up behind them and moves in. Dean grabs the shotgun and fires at it but without any effects. Michael gets in the police car and drives off, yelling at Rod that the Winchesters are innocent. The ghost Impala chases after him but Rod dismisses the entire thing as a con that the Winchesters are running. Before he can take them in, they hear a crash and go to investigate. Michael's car has spun out of control on a tight curve and crashed, killing Rod's brother instantly.
Rod locks the Winchesters up again and tells them that he'll take care of the ghost Impala on his own. Dean says that they want to help and that they're doing it for Michael because he trusted them. Convinced, Rod releases them and they leave in the brothers' Impala. They drive to the original crash site, salt the driver's bones, and burn him and the car. However, as they go back up to the road, the ghost Impala pulls up. It sideswipes the brothers' Impala, causing a gas leak. The brothers wonder how it can still exist after they sanctified the corpse and Dean realizes that the car left skid marks which are opening a portal to the other side.
The Winchesters salt the tire treads and spread oil on the, but the ghost Impala swings around and comes at them, forcing the brothers to drive away. As they drive, they leave a trail of gas behind. As the ghost car closes in, Rod warns the brothers that they're approaching the curve where Michael died and have to slow down. As Dean tries to slow down, Michael's ghost drives the police car out of the forest and rams the Impala. Both spectral cars go off the road in a burst of unearthly light. When Rod and the Winchesters drive back, they see Michael's ghost standing at the side of the road. Rod goes to his brother and, crying, says that he doesn't know what he'll do without him. Michael's spirit brushes the tears from Rod's face and then fades away, smiling. Dean kicks a piece of the burning wreckage onto the gas trail, and the flames go back up the road and destroy the skid marks.
Later, Rod releases the Winchesters and tells them that he's ready to pay the price for what he did two years ago. As he removes his badge and walks back to town, Dean tells him that Michael would be proud of him.