On the night of July 4th, five young friends—Ava, Danica, Milo, Teddy, and Stevie—gather in the coastal town of Southport to celebrate an engagement. After a night of partying and drinking, they drive up a dark cliffside road, where a reckless moment leads to a fatal accident: they hit and kill a man named Sam Cooper. Fearful of the consequences, the group decides to cover it up and swear never to speak of it again.
A year later, as Danica prepares for her wedding, she receives an anonymous note with a chilling message: “I know what you did last summer.” One by one, the group members are hunted by a figure wearing a black rain slicker and wielding a hook. Panic and paranoia set in as they realize that someone knows their secret—and is out for blood. The once-tight bond between them starts to unravel as guilt and suspicion rise.
In desperation, Ava reaches out to Julie James and Ray Bronson, survivors of a similar massacre years ago in the same town. Now older and more cautious, Julie and Ray try to guide the new generation through the nightmare, offering advice and warnings based on their own traumatic past. Their involvement deepens the mystery and adds emotional weight to the unfolding horror.
As the killer draws closer, a shocking truth is revealed: Stevie, one of the original five, is behind the murders, seeking revenge for being betrayed after the accident. But in a final twist, Ray is also revealed to be a second killer, furious that the town has forgotten its bloody history. The climax takes place aboard a boat, where Ava fights for her life and ultimately defeats Ray with a speargun, ending the killing spree.
In the aftermath, Ava and Danica survive, though scarred by what they’ve endured. Stevie also survives, setting the stage for future danger. A final scene teases more to come, as Julie visits a former friend and finds her marked as the next target. The story ends with a sense of unease, suggesting that some secrets never stay buried—and vengeance never truly dies.