During a high school track meet at Midvale High School, Laura Ramstead, after being pushed by Coach Michaels, collapses and dies after crossing the finish line.
Two months later, on the day before graduation day, Anne Ramstead, a U.S. Navy officer and Laura’s older sister, returns to her hometown in order to take part in the high school graduation ceremony in honor of her sister. When she arrives in town, she watches a girl in a track uniform, Paula, running down the street and into the woods.
Paula is followed and killed by someone wearing black gloves and holding a stopwatch, who stops the stopwatch at 30 seconds. At the high school, the killer steals a photo of the track team with Laura’s face crossed out. The killer then crosses out Paula’s face.
Meanwhile, Anne arrives home and discusses Laura’s death with her mother, and also states that she is planning to leave after graduation day. Anne heads upstairs and unpacks, her items including a grey sweatshirt and a pair of black gloves.
Another track member, Sally (Denise Cheshire), walks through the woods and encounters Anne, who is heading to the auditorium as a special guest for the graduation rehearsal. After the rehearsal, Anne visits Kevin (E. Danny Murphy), who was Laura’s boyfriend, and he shares a photo album of Laura. Anne gives Kevin one of Laura’s track medals.
Later that day, Sally, while changing into gymnastics clothes, is scared when the lights suddenly shut off and she runs into Doris (Vanna White) and Joanna (Karen Abbott). Sally, now unfocused, is unable to perform her uneven bar routine for a school photographer and is harshly reprimanded by Coach Michaels. During her routine, we cut to a shot of the team photo, and a black-gloved hand crosses off Sally’s face. After several failed attempts of her routine, Sally runs off to the locker room where she is impaled with a sword by the killer, who is now seen wearing fencing attire. The killer stops the stopwatch at 30 seconds.
In the music room, track member Dolores (Linnea Quigley) seduces Mr. Roberts in order to avoid having to go to summer school. At the same time, Principal Guglione (Michael Pataki) slices an apple with a knife, which he puts in a desk drawer that contains a stopwatch and several other knives.
In the woods, Dolores and fellow track team members Tony are confronted by Officer MacGregor while smoking a joint. They run off to the high school, where Dolores is found by Coach Michaels. He reveals that he is upset about being blamed for Laura’s death, when in reality she died because of a blood clot in her heart.
Track team member Ralph, who carries a football, runs into Doris and Joanna in the woods. They take his ball from him and accidentally throw it into the woods before running off. While looking for the ball, Ralph is confronted by the killer, who throws it back at him with a metal spike attached. Ralph is impaled by the spike and dies. A black-gloved hand stops the stopwatch at 30 seconds and crosses Ralph’s face off the team photo.
Later that night, the band plays loudly at the graduation dance held at the high school. After dancing for a while, Dolores and Tony escape out to the woods, before he excuses himself to relieve himself. While Tony is urinating, the killer sneaks up behind him and decapitates him. When Dolores grows worried, she goes looking for him and is horrified to find his dismembered head—and the killer. The killer chases after Dolores, but her screams go unheard. After a prolonged chase, Dolores stumbles and is caught by the killer. As the band’s song ends, the killer hacks at Dolores with the sword. A black-gloved hand stops a stopwatch at 30 seconds.
The next morning, Mr. Guglione fields phone calls from the worried parents of Paula, Sally, Tony, and Dolores, who did not come home the previous night. He is then visited by Inspector Halliday (Carmen Argenziano) and Guglione explains that their absence is no cause for concern. After leaving Guglione, Inspector Halliday directs Officer MacGregor to file a report on the missing teenagers.
At the track field, track member Pete runs to attempt a pole vault. However, the pads in the pole vault pit have been replaced by steel spikes and he is killed upon impact. A black-gloved hand stops a stopwatch at 30 seconds.
Back at the school wood shop, Inspector Halliday questions an angry Coach Michaels, who claims that he was fired due to negative publicity and the accusations of being responsible for Laura’s death. In the locker room, Doris and Joanne discover Sally’s body in a locker, which prompts Coach Michaels and Kevin to the run to the locker room. Kevin accuses Coach Michaels of being the killer, which results in a fight and Coach Michaels subduing Kevin before fleeing the scene. Anne, Inspector Halliday, and MacGregor arrive and find the team photo with the faces of all of the team members (except for Kevin’s) crossed out. As Inspector Halliday asks Anne about the photo, Kevin runs off after Coach Michaels.
In the woods, Kevin catches up to Coach Michaels and confronts him. Anne and Inspector Halliday are close behind trying to find them. Coach Michaels runs off again with Kevin close behind, and stumbles across Ralph’s body. He tries to explain to Kevin that he isn’t the killer, at which point Kevin reveals that he has been killing the track team, and will now kill Coach Michaels, because he blames the entire track team for Laura’s death, whom he planned to marry after graduation. Kevin starts a stopwatch, pulls out a knife, and attacks Coach Michaels. Kevin is disarmed during the struggle, and Coach Michaels picks up the knife. At that moment, Inspector Halliday sees Coach Michaels standing over Kevin with the knife in his hand. Inspector Halliday shoots Coach Michaels and Kevin lies that Coach Michaels was going to kill him.
A short time later, Anne is speaking with Guglione’s secretary and discovers that Kevin has been lying to her. She goes to Kevin’s house and finds Laura’s corpse in his room, sitting in a chair and wearing a graduation cap and gown. Kevin believes that Anne will take Laura away from him and attacks her, leading to him falling through a window with Laura’s body. Anne runs away and ends up at the high school track field, where Kevin finds and attacks her. Their struggle leads them under the bleachers, where Anne is horrified to see Dolores’ dismembered head and Pete’s spike-riddled body hanging in a storage shed. As the fight continues, Kevin is ultimately pushed into the spikes by Anne and is seemingly killed.
After giving her statement to the police, a traumatized Anne returns home that night and hallucinates an undead Kevin in her room, when in reality it is just her drunk stepfather Ronald. The next morning, Anne impassively says goodbye and leaves the town in a taxi while the Graduation Day banner hangs over the main street.