I Know What You Did Last Summer is a 2018 horror film and a re-imagining of the 1997 film while also being more true to the 1973 book of the same name.
On the Fourth of July 2017 in the small town of Southport, four high-school seniors - popular cheerleader Julie, her longtime boyfriend Ray, best friend Helen and Helen's boyfriend Barry - attend a party in the mountains after Helen is crowned 'Croaker Queen' in the towns beauty pageant, revealing her intentions to graduate and then head to New York to become a fashion model.
The group celebrate and enjoy the party, talking about their futures and how nothing will ever separate them. A boy from their school, Jesse, drunkenly comes onto Julie admitting he has always had a crush on her but she politely rejects him. Julie confesses to Ray that she's finally ready to lose her virginity to him and they have sex in an upstairs bedroom. Helen's envious and cruel sister Elsa tells Helen that she'll have to leave early because she won't be opening their family shop in the morning and Helen will have to do it. At the same time Barry gets drunk and makes a fool of himself, starting fights with other people at the party. Helen calms him down and they decide to leave alongside Julie and Ray.
Ray drives while Barry and Helen make out in the backseat. As they drive Barry's drunken antics distract and annoy Ray. Julie and Ray look at each other affectionately, Ray looking away from the road for a few moments before Julie screams and he hits something, swerving off to the side of the road. Helen's face is cut in the crash and Ray injures his leg but they are otherwise ok. The group leave the car to investigate and find a young boy wearing a rain slicker in the middle of the road next to a bicycle, near death. Ray tries to help him and they are about to call for help when he suddenly dies from his injuries. The group panic, Julie saying that they need to contact the authorities whereas Barry says they can't because they'll go to prison as they are all intoxicated.
Helen is unsure but ultimately sides with Barry, telling Julie that it was an accident. Ray remains silent as Julie lectures them, saying they can't just leave him on the road. Barry agrees and says they need to hide his body and scares Ray into going along with it, saying their life would be over in prison and that it was just an accident. Julie, disgusted, refuses to help move the body but goes with them as they hide the boys body in the field near the crash site. Julie points back to the road and they see Jesse standing next to his car at the roadside. He asks if everything is ok and they tell him everything is fine before he drives off. The group make a pact to carry the secret to their graves.
A year later and the group have drifted apart. Julie is attending a college in a neighboring state and is a social outcast, Ray is working in the town as a fisherman, Helen went to New York to become a model and Barry is attending a local college. Julie returns home to Southport after finding out over the phone from her mother that her father has died from a heart attack and his funeral is in a few days. She fearfully returns to Southport and it's revealed through an argument with her mother that Julie hasn't visited them in months and that she takes medication for anxiety and depression. After a particularly bad argument in which her mom, Anna, blames Julie for her father's death, Julie storms out of the house and runs into Ray, who has a slight limp since the crash which stopped him from being able to play football in college. They talk about their relationship but Julie doesn't want to get back together, telling him they can't go back to the way things were.
When she returns to her home she finds a note on the doorstep which, to her horror, says 'I Know What You Did Last Summer' alongside a missing person poster of Daniel Gregg. She panics and, not knowing what else to do, shows the note to Ray. He seems worried but tells her its probably nothing and it'll go away. She tells him it isn't nothing and that someone knows. He reminds her that only four people know so it has to be either Helen or Barry who wrote the note. Ray tells her that Helen is working in her families store and has been for some months.
Julie visits Helen at the store and runs into Elsa who is Helen's boss. Elsa insults and mocks Helen, who is delighted to see Julie after so long. Julie asks why she isn't in New York and Helen tells her it didn't work out. Elsa hovers around them so Helen takes her break and Julie shows her the note. Helen is startled and tells Julie it has to be Barry, who she has since split up with after he cheated on her and she moved to New York. Julie tells her they need to ask Barry and Helen reluctantly agrees to go with her. They visit Barry at his University fraternity house he's living in and he dismisses the note, saying anyone who did know of their crime would go to the police instead of leaving notes. Julie wanders if Jesse could be involved since he was there that night and Barry says its possible and he can go find out right now.
The trio head over to the store which Jesse owns. Barry interrogates Jesse over the letter but Jesse fights back and overpowers Barry. Jesse tells them he doesn't know anything about any letters but implies that he knows about the crash and that maybe its karma. The trio hastily leave. That evening Ray arrives at Julie's and reveals he has been receiving threatening texts and silent phone calls from an unknown, and untraceable, number. Julie breaks down in tears, but Ray tells her that they will get to the bottom of what's happening.
The next day Julie attends her fathers funeral alongside Helen, Ray and, to Helen's surprise, Barry. Julie and Ray exchange longing looks throughout while Helen and Barry have a heart to heart in the graveyard afterwards although Barry remains somewhat distant. Helen tells him that he never opens up, is too distant, and that's why it'll never work between them. Sheriff Thomas Cox, Barry's father, offers to give Helen a lift home. On the way he tells her that Barry really likes her and that he'd like her to be Barry's future wife, saying he needs stability and even offering to pay her. Helen refuses and leaves the car after the Sheriff calls her a whore.
Julie, still receiving silent phone calls from an unknown number, runs into Deputy Carl Harrison, a transferred police officer, who gives her his condolences, telling her that he knew her father well. She also sees Jesse at the funeral and he apologies for the way he was earlier and offers to buy her lunch. At a cafe Julie explains how everything has changed since that night and she no longer recognizes herself. Jesse admits he always had a crush on her in high school and that he wishes he didn't have to see her like this. Julie tells him she didn't really know him in high school but still agrees to seeing him a second time and kisses him on the cheek before leaving.
That evening Barry gets drunk once again and says goodbye to his buddies, returning to his frat house from the bar. Inside he receives text messages from Helen, telling him she'd like to try again and to meet her on the football field across from the frat house. Drunk, he stumbles into the middle of the fog covered football field and rings Helen's number, only to hear the phone ring behind him. As he turns around a figure wearing a black rain slicker emerges from the fog wielding a baseball bat and quickly attacks him, hitting him across the face. He dodges another swing and defends himself, managing to hit the figure twice before his leg is struck and he falls to the ground. While attempting to crawl away his leg is broken with the bat and he is beaten to a pulp. The next morning he is found naked, battered and bloodied, tied to the goal post, and is quickly rushed to hospital.
Julie, Helen and Ray all arrive at the hospital and find Barry in intensive care. His father is also there alongside Deputy Harrison, and questions the group over the incident. Helen tells them she'll stay by his side while Julie and Ray investigate further. They contact the address on the missing person poster and find a dilapidated house in the suburbs on the outskirts of the town. The house is empty and a neighbor tells them the sad story. After Daniel vanished his mother, Vera, suffered sever depression and suicidal bouts. Eventually Vera succeeded in committing suicide by slashing her wrists in a bathtub. Her husband and Daniel's father was devastated and suffered a stroke, leading to Megan Gregg, Daniel's older sister, being forced to drop out of college to care for her father. They were forced to move due to money problems and a lack of facilities for the father and now live further up the mountains. She also reveals that Daniel's older brother went AWOL from the army after an incident and hasn't been seen since.
At the hospital Barry finally wakes up and speaks to Helen who promises to remain by his side. He tells her the person was wearing a black rain slicker, similar to the one Daniel was wearing when he died. They then kiss and Helen asks him to accompany her to the parade for safety and he agrees despite the broken leg. Sheriff Thomas criticizes his son over being attacked, saying he should have beaten the attacker. Helen stands up for Barry and tells Thomas off, saying that it's because of him that Barry has had a string of relationships with random women and why he is emotionally repressed. She tells him that he can't buy her and that if he continues to harass her and Barry she will report him for money laundering. Thomas tells her she doesn't know who she is dealing with and ejects from the hospital, telling Barry that she's not good for him.
The next day Julie meets up with Jesse again and they go for a romantic walk. He tells her about how his parents divorced and that he now has to work twice as hard to support himself and his family. Julie sympathizes with him and speaks of the arguments with her mother before they look out over the beach. They almost kiss but Julie pulls away, telling him she still likes Ray. He argues with her over this, saying she hasn't changed at all. She tries to tell him she has but he leaves, telling her that she and Ray deserve each other.
Helen and Elsa argue again at their home with Elsa mocking Helen, telling her that she failed in New York because no one wanted a model with a hideous scar and that she'll never make anything out of her life. Helen slaps Elsa but immediately apologizes. Elsa tells her she hates her and deserves everything that's coming to her. Helen tries to question her over this but Elsa locks her bedroom door and sobs uncontrollably as Helen pounds on the door. Julie arrives and tells Helen she needs to talk. The two speak about Lucas and Helen jokingly teases her before saying that he seems odd. Julie admits she still likes Ray and Helen encourages her to speak to him, which she agrees. Helen tells Julie she thinks Elsa knows more about this but can't get anything out of her. They decide to follow Elsa the next day, hoping she;ll lead them to the person targeting them.
Elsa leads them to a house situated in the mountains, not far from where Daniel died. They watch as Elsa talks with a young woman before leaving. They then move in, pretending to be lost and in need of directions. The woman, Megan Gregg, lets them stay a while to rest. While there they gently question her about her family and witness Megan feeding her father, who is completely paralyzed from the neck down. Megan tells them she could never leave him in a care home after what happened. Julie pushes questions about visitors and Megan admits a girl comes to see her (Elsa) and that the girl is a volunteer at a charity helping soldiers and that she believes she met her brother there, although she hasn't seen him in months since he left the army.
The two leave, in order to get ready for the parade the following day. Barry is now able to leave the hospital, although is encouraged to stay longer. He has an argument with his father that night and disowns him, revealing his intentions to leave town with Helen. Ray and Julie get closer and Julie reveals she loves Ray and wants to be with him. They have sex that night and Ray considers proposing to her with a ring he bought but decides its too soon. Julie receives a message with a picture of Daniel's bike and 'Tomorrow it ends'. Ray consoles her and promises he won't let anything happen. Julie has a nightmare that night of being chased by the attacker before being forced to watch Ray die and all of her friends being lowered into the ground along with her father and Daniel appearing, blaming her for their deaths.
The next day is the Fourth of July and Helen is getting ready for the parade. While getting ready she finds her phone in Elsa's room and confronts her, saying that Barry received messages from her phone before he was attacked. Elsa smugly tells her to enjoy her day before leaving. Helen goes to the police station and sees Deputy Harrison although she decides not to say anything when the Sheriff appears and quickly leaves. She then joins the float and sits atop it while Barry watches over her, making sure the attacker isn't near.
Julie continues investigating but is still puzzled over something. Lucas arrives at her doorstep and apologizes for the way he reacted, hoping that they can still be friends. She agrees and he tells her he hopes to see her at the parade that night. She heads back to Megan's to question her further, trying and failing to contact Ray. Meanwhile, the pageant is well underway as Helen sits on the stage, with Barry watching from the balcony. He sends her messages, joking about the performances before telling her he intends on taking her away from Southport. She agrees to go with him. Just then, Barry hears a noise behind him but doesn't see anyone. The figure emerges from the shadows and picks up hook, attacking Barry when he turns around again. The hook is shoved up through Barry's chin and out his mouth, stopping him from calling for help. Helen witnesses this and screams, running out into the crowd to try and help him. Barry attempts to defend himself but has his leg broken again with a metal pipe before the hook is ripped out, destroying most of his jaw. He fights back but is dragged back into the shadows and slashed repeatedly with the hook, killing him.
Helen pushes through the crowd but is stopped by the Sheriff. She tells him that his son is being killed and they go and investigate. However, no body is seen anywhere and the Sheriff doesn't find any blood. Helen screams at him, saying that Barry's dead because of him. He tells her she's going back to the station and arrests her when she refuses to go. Back at Megan's, Julie questions her, asking why Daniel was up in the mountains on his own. Megan asks how she would know that. Julie theorizes that Vera, being on medication even prior to Daniel's vanishing, left him in the mountains to die on his own, as she suffered with extensive postnatal depression for years. Megan asks what she means by Daniel's death, right before Daniel, still very alive, walks into the living room. Megan tells her that, yes, Daniel was injured in a hit n run but he survived the incident, being in a coma for four months, after her older brother found him on the side of the road. Her mother did leave him at the side of the road and that was one of the reasons she later committed suicide, guilt over what happened. A shocked Julie leaves, finally putting the pieces together after seeing a family photo of Daniel after the accident.
Helen is put into the back of the police car by Thomas, being forced to give up her crown as well. As they drive Helen cries, blaming Thomas for Barry's death. Thomas tells her Barry is alive as they are forced to go an alternate route due to the parade, and drive down an alleyway. Thomas stops the car as Helen insults him and tells her to shut up or else. She continues blaming him and he decides to ring Barry's phone to prove to her he's still alive. The phone rings and they both hear it. The ringing is coming from the trunk of the police car. Thomas get out to investigate but Helen warns him not to. Thomas opens the booth of the car and finds Barry's mutilated and mangled body staring back at him. Suddenly, the figure jumps out from booth as well, tasering him. Thomas stumbles backwards as the figure emerges and attacks him again, grabbing and throwing him against a wall and, after a brief struggle, slashing his throat with the same hook from before, causing him to bleed to death.
Helen escapes through the booth of the car, crawling over Barry's body and running through the alley, away from the killer. Julie races back towards the town, still trying to ring Ray and failing. Helen is chased through several alleys and across a park, with the killer in tow. She makes it to her family store and finds Elsa inside. She barely makes it inside before telling Elsa what happened. Elsa is shocked, saying that wasn't part of the plan. A confused Helen begs her to tell her what is going on. Elsa admits that she knows who the attacker is and that she's been seeing him for a while but they were never meant to kill anyone. She only wanted to humiliate and scare Helen away from the town and out of her life so she could be the family favourite once again. Helen calls her insane and tells her she's calling the police. Elsa begs her not to, saying she knows the attacker is and is about to say their name when the figure emerges from behind a mannequin and stabs her in the back with the hook, ripping it upwards and lifting her into the air before easily tossing her aside.
Helen flees upstairs and locks herself in a room before trying to call the police. Deputy Harrison answers but the attacker breaks the door down and she is forced to leap out of a window, barely avoiding the killer's hook. She flees once more. Julie makes it to where the pageant was being held but finds the hall empty. She decides to head to Ray's workplace and see if he's there. Helen flees through an alley and down to the side of a lake where she witnesses the fireworks going off on the other side of the lake with people celebrating. She starts running again but is cornered by the killer. She is grabbed and fights back, freeing herself from the killer's grasp. However, as she screams for help she is grabbed a second time and stabbed in the chest before being thrown into the lake. She hits her head and, dazed, looks around for the killer. She tries swimming to the other side but the killer emerges from the water and attacks again, slashing and stabbing her while in the water. She screams for help as the killer begins drowning her but no one can hear her. She manages to see her killers face before she is stabbed and slashed several more times and sinks under the water, finally dead. The killer emerges from the water carrying her body.
Julie makes it to where Ray works at the quays and finds the place thrashed. She goes onto his boat, finding the lights on, and searches for him. She finds him tied up and beaten with a missing persons poster of Daniel stuck to him. Julie realizes the killer is in the room and says that she knows Lucas is behind all of this. Lucas emerged from the shadows, clapping. She tells him she knows he was adopted into the Gregg family and that his birth name was Ben Willis. She then asks him why he would do all this and he tells her it's their fault his adoptive mother died, that she killed herself over the guilt of Daniel being hit by their car, and that they left his brother to die. Julie tells him that doesn't give him reason to attack them and he tells her that people like them think they can get away with anything if they have money, that the police didn't car that an African-american child was hit and barely investigated it whereas they spent months looking into a similar hit n run incident on a white girl. He tells her they will all pay for what happened and set the boat alight, being attacking her.
Julie fights back and hits him with a hammer before being forced to flee into another part of the boat. Ray wakes up and begins to try and free himself. Julie is pursued through the boat, defending herself from Lucas while also finding the bodies of Helen and Barry aboard the boat. She managed to injure him and knock him overboard with Ray's help although he crawls back on and stabs Ray in the back, presumably killing him. Julie flees the boat and runs towards the parade while Ray struggles to his feet. She is pursued through an alley before making it into the crowds where Lucas chases after her. She is almost stabbed several times before she climbs onto the float. The killer attacks her again, causing the crowd to flee in all directions. Ray emerges and races towards the float with a speargun. Lucas still tries to kill Julie, slashing her leg. As he raises the hook to kill her, Ray shoots a spear right through his back and out his stomach, causing him to drop the hook. Julie quickly picks it up and plunges it into his chest. Julie and Ray embrace each other as the blood pools around Lucas' body.
Two months later, Julie and Anna are on much better terms as Julie is about to go back to college. Julie and Ray are now in a relationship again and they leave flowers on Helen and Barry's graves, along with Vera Gregg's. They kiss and Ray asks if she's ready, him going to live with her near the college. She tells him she forgot one thing and goes back to her house, going to her bedroom and taking the necklace her father gave her. However, Julie notices a window is ajar and heavy steam coming from the bathroom with the light on. She calls out for her mother but doesn't get an answer. She slowly opens the bathroom door before the film cuts to black.
- Hailee Steinfeld as Julie James
- Dylan O'Brien as Ray Bronson
- Zara Larsson as Helen Rivers
- Ansel Elgort as Barry Cox
- Shannon Purser as Elsa Rivers
- Dylan Minnette as Lucas Wilson/Ben Willis
- Jeffrey Dean Morgan as Sheriff Thomas Cox
- Maura Tierney as Anna James
- Keke Palmer as Megan Gregg
- Scoot McNairy as Deputy Carl Harrison
- Miles Brown as Daniel Gregg
- Barry Cox - Hooked in the jaw, Beaten, Leg Broken with metal pipe, Hook ripped out destroying his jaw and slashed to death off-screen.
- Sheriff Thomas Cox - Tasered in the chest, Beaten, Thrown against a wall and throat slashed with hook.
- Elsa Rivers - Stabbed in the back with the hook, hook ripped upwards and lifted into air before being thrown aside.
- Helen Rivers - Stabbed/slashed with hook repeatedly, thrown into lake and drowned while being stabbed/slashed with the hook.
- Lucas Wilson/Ben Willis - Hit with a hammer twice, knocked overboard, Stabbed in the hand with a knife, shot through the back/stomach with a speargun and stabbed in the chest with the hook.
- Anna James (?) - Possibly killed in the bathtub by either herself or another killer.