During a deadly endurance race, a driver faces the trauma of a past accident.

A year after being involved in an accident in the famed French twenty-four hour car race at Le Mans that killed a Swiss driver, American Michael Delaney returns to the endurance contest to drive for the Porsche team. The day-long race draws an enormous audience that crowds around the inner portion of the thirteen-kilometer circuit. Although the main competitors are prototype racing cars designed by Porsche and Ferrari, which each have four cars entered in the race, a variety of cars compete simultaneously. Each of the cars has two drivers who alternate during the day of racing. Michael is assigned by Porsche team leader David Townsend to Porsche number 20 with a co-driver, German Bruno Frohm. The main competition is expected to come from Michael's longtime rival, German Erich Stahler in Ferrari number 8. On his way to the track, Michael is startled to run into Lisa Belgetti, the widow of the driver killed the previous year. The race announcer welcomes Michael's return to Le Mans and predicts a close competition between him and Stahler. With tension and anticipation, the four o'clock start time ticks down and the competition begins with the shriek of numerous precision-tuned cars. After a couple of hours, Michael pulls into the pit to transfer driving to Frohm. Returning to his trailer to take a brief rest, Michael runs into Lisa and makes solicitous inquiries about her well-being. Meanwhile, Porsche 21 also changes drivers and the car's German driver, Johann Ritter, returns to his trailer, where he meets his wife Anna and declares that he is content to retire after the race. As dusk approaches it begins to rain, but the race continues. When the fourth Porsche entry experiences engine failure and must withdraw, several reporters approach Michael to inquire if this unexpected loss puts the Ferrari team in the lead. Michael and Stahler run into each other heading back to the pit and dismiss press reports depicting their competition as personal. Each driver takes over for the next portion of the race even as mechanics and other drivers wonder aloud why Townsend has not ordered that rain tires be put on the Porsches. The cars make several long laps in the skies darkened by the pouring rain before both main teams recall their drivers to change tires. A minor accident on the course is announced and Lisa listens tensely. A few hours later, unable to see much of the competition, Lisa wanders over to the racing village and its carnival-like atmosphere, where the high-pitched whines of the racing cars are never far away. In the dead of night, Michael and Frohm switch again. Later in the cafeteria, Michael spots Lisa and sits with her to ask how she has managed since her husband's death. Curious, Michael inquires why she has returned to Le Mans and Lisa responds that it is something personal that she needed to do. At five in the morning as dawn approaches, Michael resumes driving as the rain lightens. After several more laps, Stahler experiences a spin-out on the slick roadway, but he and his car are undamaged. Although yellow warning flags are immediately posted, Ferrari 7, driven by Frenchman Claude Aurac, comes upon Stahler's stopped car at high speed and, trying to avoid a collision, loses control of his car and smashes into the railing, which sends the car catapulting into the brush. Even though the accident shreds the body of the car, Aurac is able to jump out of the wreckage, stumbling a few feet before the Ferrari explodes, knocking him several yards. On the roadway, Michael glimpses the fireball in the distance and in the split second that his eyes flicker toward it, he comes upon a slower car in his lane. Startled, he wrenches the wheel, which sends his Porsche careening into a rail and back across the road into another railing. The car spins out of control and is wrecked, but although badly shaken, Michael is unhurt. Stahler rejoins the race as a helicopter transports the severely injured Aurac to the infirmary. Upon hearing the announcement that Ferrari 7 and Porsche 20 are out of the race due to an accident, Lisa hastens to the infirmary where she numbly watches Aurac's treatment and his emergency transport to a hospital. Meanwhile, Michael is examined carefully and approved for release. Spotting Lisa being overwhelmed by reporters, he escorts her to a cab. Going out to the pits to watch the latest race results, Michael meets Townsend and admits that his error caused the destruction of Porsche 20. After watching the race for some time, Michael returns to his trailer, only to find that Lisa has returned and is loitering nearby, drained and exhausted. He invites her inside for some coffee and upon seeing her continued distress over Aurac, reminds her that racing is a "blood sport." When Lisa asks if people should instead risk their lives for something important, Michael points out that many people spend their entire lives doing things poorly and race driving does not allow that. Michael then adds that for him, driving is life and the time before and after is just waiting. The race continues throughout the morning into the afternoon, when Porsche 21, driven by Ritter, comes into the pit with rear suspension trouble. Ferrari 8 pulls in for Stahler to take the wheel for the final portion of the race. As the Porsche mechanics anxiously struggle to repair Porsche 21, Stahler is unable to restart his car. Hearing the announcement that teammate Larry Wilson in Porsche 22 has taken over second place behind Ferrari 5, Townsend abruptly approaches Michael and asks him to take over from Ritter in Porsche 21. Although surprised, Michael agrees and Townsend declares that Porsche must win. Ritter takes the news well, but admits to Anna that this is not how he intended to retire. Stahler's car restarts and he roars off, with Michael following moments later. As Stahler and Michael jockey for position, Ferrari 5 is forced out of the race with a flat tire. As the four o'clock deadline approaches, Michael continues to harass Stahler in the backstretch, keeping the German from catching up with Porsche 22. The race ends with Wilson's team car 22 winning, Porsche 21 in second place and Ferrari 8 in third. Back in the pits, Michael and Stahler salute each other as the crowd cheers for the victors. Seeing Lisa waiting, Michael makes his way to her.