The movie opens with Wendy Christensen (Mary Elizabeth Winstead), an obsessive-compulsive driven high school graduate from McKinley High, photographing her friends on a ride called the "High Dive". Shortly after she takes their picture, she notices the letter "V" missing out of the ride name, but thinks nothing of it. As the beginning of the movie progresses, we're introduced to several characters, including Wendy's boyfriend Jason Wise (Jesse Moss), her best friend Carrie Dreyer (Gina Holden), and her boyfriend Kevin Fischer (Ryan Merriman), as well as several other characters; the jock Lewis Romero (Texas Battle), the valley-girlesque Ashley Freund and Ashlyn Halperin (Chelan Simmons and Crystal Lowe), the social outcasts Ian McKinley and Erin Ulmer (Kris Lemche and Alexz Johnson), as well as Wendy's attitude-laden sister Julie (Amanda Crew) and the troublesome alumnus Frankie Cheeks (Sam Easton). They all begin to make their way to the roller coaster, which has a demon-like figure at the front and a dark, foreboding voice warning them of the ride ahead. This causes Wendy to begin feeling uneasy, even as she's taking pictures for the yearbook.
The group begins boarding onto the roller coaster, with Jason getting divided from everyone else, as he sits in the front car with Carrie, while the others sit in the back. Lewis is attended to by the ride attendant to adjust his shoulder pads, and this sets off a slight leak in a hydraulic pipe on the car, unnoticed by staff. Frankie hides a video camera in his pocket as Wendy's camera is pocketed by Kevin, sitting next to her. The ride begins and soon turmoil erupts as the leak continues and Frankie's camera is knocked away by Ashley, wrapping itself around the track. It's run over, causing the leak to become worse and the ride's shoulder belts to become loosened. One car suddenly jars entirely off the track, and others begin dropping off left and right. The ride suddenly stops upside down, forcing Ian and Erin to hang and eventually fall to their deaths. Kevin and Wendy motion the ride to go backward, but in doing so, Kevin is cut in half and Wendy is dumped onto the track...
Then Wendy wakes up and realizes it is all a premonition. She's still sitting in the car as it gets ready to move. She becomes hysterical and demands to be let off, and the attendant releases all the seats in the rear car. Wendy and Kevin exit, and soon the others follow, out of annoyance (and because Lewis starts a fight with Kevin). Jason asks to be let off as well, but the ride continues with him and the people in the front car still sitting in it. Attendees lead a terribly upset Wendy outside and the coaster crashes, as predicted, leading to the deaths of Jason, Carrie, and several others.
Some time afterwards, Wendy is at the school and is confronted by Kevin, concerned about her and the loss of Jason and Carrie. Wendy insists to be left alone. Ashley and Ashlyn invite her to a tanning session, and she takes their phone number. As she makes her way to her car, Kevin explains that this has happened before, with flight 180 and the seven people who got off and mysteriously died. Wendy drives off as thunder booms overhead.
Ashley and Ashlyn head over to their favorite tanning salon, hoping to bronze up for the graduation. They both have slurpees, and the owner insists they throw them away, as he heads off to complete a phone call. Ashley merely pretends to throw her drink away, and they both head to the tanning room, where they proceed to disrobe. Ashley sets her drink right above a cooling unit of the tanning beds. She also reaches for a CD, leaning on a shelf and slightly loosening it on the side. The owner heads out the door, with only a tube of lotion holding it open. However, the lotion squirts out, and the door closes shut and locks.
Meanwhile, Wendy is looking over the photos she took the night of the accident, after promising Julie to borrow the camera to her. Julie lends her a bracelet left behind as a family heirloom. It's then she notices a photo of Jason with a foreshadowing of the coaster behind him as it is about to hit his head, and gets an eerie feeling as the light bulb dims in and out. She then looks at the picture of Ashley and Ashlyn, which appears to be over-saturated, reminiscent of flames. She finds Ashley's number and proceeds to dial.
Back at the tanning salon, Ashley's slurpee has begun to leave a water residue, which leaks into the cooling unit and forces the temperature to rise slightly. As the girls seem to notice this, a cooling fan causes a coat rack to to fall over and knock over a plant, causing the plant to fall onto the shelf and collapse. The panel from the self slides right between the handles of both beds, locking Ashley and Ashlyn in as the temperature rapidly rises. Both girls wince and scream in agony as the bulbs begin overheating and eventually breaking, causing their skin to bubble, and soon a fire breaks out, setting both beds ablaze. The owner tries to get in, but the back door is locked, and he also locked the front. The girls are burned alive in the blazing tanning beds.
The next scene is at their funeral, where Ian begins questioning the preacher's comments about the equality of death and is led off by Lewis and Kevin. Afterward, Kevin finds Wendy kneeling at Jason's grave, and she begins to show him pictures that depict what's going to happen beforehand, including a picture showing a plane's shadow about to crash into the Twin Towers in New York. Suddenly, a strange wind blows over both of them, and Kevin tells Wendy he's going to get her some food.
The two go to a local drive-thru restaurant, unaware that Frankie is ahead of them in his sports coupe. On the way, the two almost hit a truck in their vehicle, forcing the driver to jump aside. They get to the drive-thru of the restaurant, noticing a vehicle is pulling behind them and also to the side, blocking Wendy's exit. The sign also shows a the word "control" glitching out, and soon the radio kicks on, playing "Turn Around, Look at Me" by the Lettermen. Suddenly, Wendy and Kevin notice a driverless truck coming their way. They can't escape the vehicle, and they unknowingly honk at Frankie to move aside, only to have him flip them off. The couple behind them move their car, and they smash the windshield and jump out of the vehicle before the runaway truck hits it. The vehicles collide, forcing Kevin's car to eject its engine out of the front. It slides along the back of Frankie's car, and the fan cuts right into the back of his head, killing him. Wendy and Kevin go to check who the dead person was, and a "jolt" moment occurs when the fan spins one last time, splattering Frankie's brains all over the wall.
After a talk with the coroner, Kevin and Wendy begin to calculate Death's design and who was sitting where on the roller coaster. They look over the photos and decide to pay Lewis a visit while he's in the middle of a workout. Lewis dismisses their claims and proceeds with his workout, even as Wendy points out to Kevin that his photo shows a Sultan caricature with swords, a weight dropping on his head, and a crying bear in the picture. (There's a tall bear statue and a sign with loose swords in the weight room). Lewis begins to work out with the other team members around him, causing the swords above his weight machine to rattle loose. Suddenly, one of Lewis' teammates accidentally jars a tooth out of the bear's mouth, forcing a weight lifter to drop his weights. Lewis stops for a moment, and the swords come down, missing him and instead cutting off a cable on the machine he's working on, unbeknown to Wendy, Kevin and Lewis. Lewis takes this moment of apparent victory over Death and lifts the weights one more time, only to have the the two weights on top smash his head to bits.
After a conversation about the bizarre occurrences, Wendy and Kevin make their way to a hardware store where Ian and Erin work. Ian is seen shooting at pigeons with a nail gun, then sets it down. He then makes light of the events that are occurring and makes fun with Wendy and Kevin. However, soon some accidents are set into motion and a forklift begins moving and knocking objects around, and it forces it to start lifting on a wall loaded with objects, including sharpened stakes and pieces of flat plywood. As Ian theorizes about Death's design, Wendy notices the stakes, and Kevin saves him as various items begin falling down. The plywood boards soon start stacking on top of each other, and a piece of wood flies off and penentrates a bag of sawdust, blinding Erin. She ends up falling backwards and lands with the back of her head against a nail gun, and nine rounds end up getting fired through her head and hand, killing her. Wendy, Kevin and Ian stare in horror.
After a visit to the police station and the disbelief that follows, Wendy and Kevin split up, with Ian unnoticeably looking at Wendy from his truck. Wendy ends up falling asleep at her house, and Julie comes along to take the lucky bracelet back, for good luck. Upon leaving, Wendy wakes up and realizes that Julie and her friend Perry snuck into the ride as well, upon identificating the bracelet in a photograph. She calls Kevin and informs him that his photo looks like something glaring, with bright lights. It's then that Kevin informs her that he's overlooking security at a colonial fair, complete with fireworks, and Wendy starts heading out the door to the fair. Soon, the song she heard at the drive-thru begins playing again, and she notices a vehicle following her. She almost hits a wolf in the middle of the road but continues to the fair.
Kevin notices Julie and her friends Perry (Maggie Ma) and Amber (Ecstasia Sanders) at the fair and tries to talk to her, but she runs off after being annoyed by him. Meanwhile, an actor at the fair leaves his lighting stick in front of a cannon, knocking it sideways and forcing a cannonball to run along and knock one of the firework trailer cars off balance. Wendy shows up, suspecting Kevin might be struck by fireworks. As the show at the fair starts, and fireworks begin to go off, a couple of teenagers set off some firecrackers, startling a nearby horse. The horse begins running through the crowd, dragging a wooden stake behind him. Julie ends up getting the rope tied around her neck, and almost gets impaled on a rake that the horse jumps over. Kevin, however, manages to cut her loose. It's then that Wendy asks the frantic Julie who was sitting next to her on the roller coaster, and she glances at Perry. As Perry realizes this and begins standing up, the horse, still startled, pulls a flagpole off a trailer, which launches itself into Perry's back, killing her.
After a close call with Kevin where he is nearly killed by a blazing gas leak, Julie and Wendy begin to drag him off, only to run into Ian, who thinks that he is the cause of Wendy's death (indicated by a shirt she was wearing, bearing his last name, which is also the name of their school). He confronts them as a firework cart begins wobbling and aims the fireworks right at them. The three duck as the fireworks go off, which entirely avoid Ian. Thinking he's safe and that Wendy is next, a loosened crane of a cherry picker that was struck by fireworks launches the McKinley sign downwards which cuts Ian in half. His corpse appears to be flipping off the three, and the screen fades to white.
Five months later, Wendy is shown to be in another town, starting a new life with her friends. She is on board of a subway train along with them, and starts to notice advertisements of the locations the previous deaths occurred at, as well as the "Turn Around, Look at Me" song being sung by a patron. She then gets uncomfortable and tries to exit the train, but is stopped by Julie, who also boards the train. As she does, a group of football fans drop an unfinished candy bar, which misses a trash can and falls onto the tracks, where a rat begins eating it As the doors close, Wendy can't help but notice that the train's number is "081", which, in the reflection of a mirror she is looking at, reads "180", the ominous number in the franchise. She is unnerved, but sits down to talk to Julie.
As they speak, she notices Kevin riding on the train as well, and goes over to ask why he's there. As he begins talking, she notices something is wrong as the lights begin to dim. Meanwhile, the rat chews on the candy bar, but gets too close to electricity and fries itself, causing the tracks to switch over. The train then goes haywire, and everyone panics as it flies off the tracks. Julie is obliterated by the train's wheel, and Kevin is thrown against a cracked window and is unable to move as it slowly begins to grow weaker. The window finally breaks and Kevin is jettisoned outside, screaming as he is violently ground between the train and tunnel wall. Wendy clings onto a pole, screaming, until the train crashes and she is thrown outside. Wendy sees that everyone is dead around her, and she crawls, seeing her leg is severely injured. Wendy begins crying and soon afterwards another train approaches her at full speed.
She begins screaming and just as the train is about to hit her, it is revealed to be another premonition she had while talking to Kevin - but this time, the premonition has taken place mere seconds before the accident which it depicted. Wendy alarms Kevin and Julie about the train as Kevin grabs the emergency brake. Julie and Wendy try to pry the door open as the lights begin to flash and the screen cuts to black. The last thing heard is the crashing of the subway train.