Teenager David Langham, Jr. and his friend, Clarence "Swifty" Johnson, watch from the sidelines as their classmate, Jack Blodgett, takes part in a daring illegal drag race. David is dismayed to see that his childhood sweetheart, Janie Pitts, is impressed by Jack's daredevil antics. Meanwhile, in juvenile court, Judge Langham, David's father, lectures a pair of youthful defendants and their parents on the dangers of hot-rods, citing fatality statistics. Over dinner that night, David tells his father and his older brother Joe, a police officer, that he and Swifty have gotten jobs delivering newspapers, and asks for money to buy a used car. The brothers try to convince their father of the importance of a hot-rod strip, and Judge Langham gradually comes to see the value of a sanctioned racetrack, where legal time trials can take place. Meanwhile, David buys a beat-up old car for his paper route, and while he is giving Janie a ride one day, Jack zips by them in his hot-rod. When Janie begins riding home from school with Jack, David becomes jealous and decides to convert his car to a hot-rod. He and Swifty spend a week working on the car in Swifty's garage, and as soon as the car is ready, David offers Janie a ride home. She turns him down to ride with Jack, however, so David invites another girl, Gloria, to go for a drive. Jack decides to taunt David by passing him on the highway, but, to his surprise, his car cannot overtake David's hot-rod. The next day, Jack steals David's car as a prank, intending to hide it so that David cannot pick up Janie for their date, but he accidentally hits another car. He abandons David's car, but Roberts, the man whose car he hit, takes down the license plate number and gives it to the police. When David and Swifty go to the police station to report the stolen car, the police arrest them for hit and run, and soon the story is on the front page of the paper. Joe believes David's story, but Judge Langham refuses to listen to his son's explanation. At David and Swifty's hearing, Judge Langham is about to turn the case over to another magistrate when Roberts says that David is not the boy who hit him. Tormented by a guilty conscience, Jack then stands up and confesses. After sentencing Jack, Judge Langham announces that the hot-rod strip will not be built, and orders David to get rid of his car. The next morning, David and Swifty are driving the car back to the lot when they come upon the scene of a liquor store robbery. They pursue the getaway car, attracting the notice of the police, and Joe and his partner take the call. David and Swifty follow the robber onto the highway and write down the license number, but they are pulled over by Joe, who joins them in the hot-rod. The crook is captured, and the police escort David home and tell Judge Langham what happened. Judge Langham apologizes to his son, then asks David and Swifty to discuss ideas for the racetrack with him. Later, Judge Langham presides over the dedication of the town's new timing strip, as David and Janie kiss.