Plot

Get ready for the outrageous coming-of-age love story about growing up...and blowing up. When students in their school begin exploding (literally), seniors Mara and Dylan struggle to survive in a world where each moment may be their last.

When students in their high school begin inexplicably exploding (literally...), seniors Mara (Katherine Langford) and Dylan (Charlie Plummer) struggle to survive in a world where each moment may be their last. As an unexpected romance blossoms between them, Mara and Dylan discover that when tomorrow is no longer promised, they can finally start living for today.

During a senior calculus class at Covington High, senior student Katelyn Ogden (Mellany Barros) inexplicably explodes, spraying the surrounding students and classroom with blood. The police take the class into custody during an investigation, but aside from ruling out an attack, are unable to determine the cause of the explosion.

During custody, senior student Mara Carlyle (Katherine Langford) suggests to the class that it could happen again, a sentiment taken seriously by her peers. Afterwards, an unknown person texts her, claiming to have had a crush on her for multiple years: Mara promptly asks for the texting person not to send a dick pic, to which the individual responds with a picture of Richard Nixon. Mara lives with her parents Angela (Piper Perabo) & Charlie (Rob Huebel).

Following Katelyn's funeral service, Mara gets high on mushrooms purchased from school dealers, Jenna (Laine MacNeil) and Joe Dalton (Clive Holloway), and goes for tea with her best friend Tess (Hayley Law); fellow student Dylan Hoevmeyer (Charlie Plummer) approaches the pair and reveals himself to be the unknown texting person with said crush on Mara. Dylan explains how he had begun thinking of life and how quickly it could end, and upon hearing Mara's suggestion of the incident repeating itself, realized that he needed to take action.

They begin seeing one another and attend a school football game and house party, although each is cut short when a jock, Perry Love, and drink server, Cranberry Bollinger, explode, respectively, sending the attendees into a panic. Classes are canceled for a while, and people begin to dub the explosions as "The Covington Curse". Dylan drives a milk truck van. The incidents attract the attention of numerous government agencies, who place FBI Agent Carla Rosetti (Yvonne Orji) on the case; she enlists Mara and Tess as aid.

While investigating the possible involvement of drugs as the cause of explosions, Mara goes for a drive with the school dealers, the Dalton twins; they explode and the car crashes. Dylan arrives and consoles a dazed Mara, before federal agents arrive in protective suits and detain them. The entire senior class is placed in observation while the government devises a "Snooze Button" pill to "cure" the students, during which multiple students explode, while many different medicines are tested on them. Realizing they should live like every day might be their last, Mara and Dylan continue seeing each other, pursuing a hedonistic lifestyle; they have sex and dance to 80s music in an old barn.

School resumes for the senior class, although the townspeople begin to fear the students and Agent Rosetti inadvertently admits to Mara that the explosions may not yet be over. While demonstrating the supposed effectiveness of the pill at a school seminar, a student explodes, triggering a chain reaction of explosions in the classroom. Dozens of students explode during the ensuing rampage, whereas Mara and Dylan are separated by the mob in a struggle to escape the building. Mara exits through a side entrance with ease and reunites with Dylan, who tells her he's glad she's still here and then explodes, injuring Mara in the process.

Following Dylan's death, a despondent Mara turns to alcohol, and in the ensuing weeks drunkenly falls out with her parents and Tess, as well as accidentally breaking Agent Rosetti's car window with a stolen bottle of whiskey. Mara also reads student comments online speculating that she might be the Covington Curse, as she was present at the scene of each occurring explosion. At the combined graduation/prom ceremony, Mara reconciles with Tess, who reveals that she is leaving town for a beach house that night and invites her to come. Believing herself to be the curse, Mara casually apologizes to the attendees for causing the explosions, but others chime in, claiming responsibility over circumstantial personal problems. Leaving the event, Mara visits Dylan's grave, and has a heart-to-heart conversation with his mother Denise (Chelah Horsdal), who convinces her to move on with her life. Mara apologizes to her parents and sobers up.

After the rampage, the next "Snooze Button" pill seems to be effective and the explosions stop anticlimactically, leaving 31 students in the senior class dead. Covington High is closed by the authorities and scheduled for demolition. Mara gains possession of Dylan's milk van and - with her parents' blessing - moves into the beach house with Tess, as they had intended to do since childhood. The film ends with Mara telling the viewers to enjoy life while it lasts, as, "[What] the fuck else can you do?"