In Modesto, California in early September 1962, on the last evening of summer vacation, recent high school graduates and longtime friends Curt Henderson and Steve Bolander meet two other friends—John Milner, the drag-racing king of the town, and Terry "The Toad" Fields—in the parking lot of the local Mel's Drive-In. Curt and Steve are scheduled to travel "Back East" the next morning to start college. Despite receiving a $2,000 scholarship from the local Moose Lodge, Curt has second thoughts about leaving Modesto. Steve gives Terry his 1958 Chevrolet Impala to care for until he returns at Christmas. Steve's girlfriend, Laurie, who is also Curt's sister, arrives in her car. Steve suggests to Laurie, who is already glum about him going to college, that they see other people while he is away in order to "strengthen" their relationship. Though not openly upset, she is displeased, which affects their interactions the rest of the evening.
Curt accompanies Steve, last year's high school student class president, and Laurie, the current head cheerleader, to the back-to-high-school sock hop. En route to the dance, Curt sees a beautiful blonde woman driving a white 1956 Ford Thunderbird: at a stoplight, she mouths the words "I love you" before disappearing around a corner. Curt becomes desperate to find her; one of his friends tells him "The Blonde" is the trophy wife of a local jeweler, but Curt doesn't believe it. After leaving the hop, Curt is coerced by a group of greasers ("The Pharaohs") into participating in an initiation rite that involves hooking a chain to a police car and ripping out its back axle. The Pharaohs tell Curt that "The Blonde" is a prostitute, but he refuses to accept that as true.
Determined to get a message to the blonde woman, Curt drives to the local radio station to ask the disc jockey "The Wolfman", who is omnipresent on the car radios, to read an on air message for her. Inside the station, Curt encounters an employee manning a console of record and cassette players, who tells him The Wolfman doesn't work at the station, and that the shows are pre-taped for replay at multiple stations. The employee accepts the message from Curt and promises to try to have The Wolfman air it. As he's leaving the station, Curt sees the employee talking into the microphone and hears the voice of The Wolfman on the air, so Curt realizes that despite the employee's earlier denials, he really is The Wolfman.
The Wolfman reads the message for The Blonde, which asks her to meet Curt at Mel's or call him at the phone booth outside. Curt is awakened by the phone's ringing early the next morning. "The Blonde" doesn't reveal her identity, but says she knows Curt and maybe they'll meet that night if he sees her cruising on her usual street. Curt replies probably not, intimating that he has decided to go to college after all.
Terry in Steve's car, and John in his yellow 1932 Ford Deuce Coupé hot rod cruise the strip of Modesto. Terry, who is normally socially inept, picks up a flirtatious and somewhat rebellious girl named Debbie. John inadvertently picks up Carol, an annoying, precocious 12-year-old who manipulates him into driving her around all night. Another drag racer, the handsome and arrogant Bob Falfa, is searching out John in order to challenge him to a race.
Steve and Laurie have a series of arguments and make-ups through the evening. They finally split and as the story lines intertwine, Bob Falfa picks up Laurie in his black 1955 Chevrolet One-Fifty Coupé. Bob finally finds John and goads him into racing. A parade of cars follows them to "Paradise Road" to watch. As Bob takes the lead, a tire blows out and causes him to lose control. His car plunges into a ditch and rolls over. Steve and John leap out of their cars and rush to the wreck while a dazed Bob and Laurie crawl out and stagger away just before it explodes. Distraught, Laurie grips Steve tightly and begs him not to leave her. He assures her that he will stay in Modesto.
At the airfield later that morning, Curt says goodbye to his parents, Laurie, Steve, John and Terry. As the plane takes off, Curt gazes out the window and sees the white Thunderbird driving in parallel to his plane's flight path.
An on-screen epilogue reveals that John is killed by a drunk driver in December 1964, Terry is reported missing in action near An Lộc in December 1965, Steve is an insurance agent in Modesto and Curt is a writer living in Canada.
