Prior to Christmas break, a young woman Emily Blunt
(listed in credits simply as "girl") accepts the idea from a cell phone texting session to use the campus "Ride Share" program as an alternative to riding the bus back home to Delaware. Finding a posting on a bulletin board, she catches a ride home from a stranger, Ashton Holmes
(listed in credits simply as "guy").
She arrives late to her ride, finding guy sleeping in his car, a late model sedan. As he pops the trunk of the car for her couple suitcases, his trunk is revealed to be overloaded with his personal belongings. He explains that he has just been "kicked out of my apartment." While he warms up the car, she rearranges his trunk to find room for her suitcase. To make room, she pulls out a random bag of his stuff from the trunk and as they drive away, the oversized shopping bag is seen sitting in the empty parking lot.
The girl's anti-social behavior is made clear as she selfishly carries on a cell phone conversation. Finally noticing the pained look on her driver's face, she hangs up her phone. He explains to her the "rules" of ride sharing, they share half the expenses and it's her responsibility to keep up a conversation while they drive. The conversation is very stilted between mismatched pair: the anti-social, loner chick and the square Catholic High School graduate driver who is majoring philosophy. Guy reveals they shared a class together. Girl says it was a huge class and she never noticed him. Guy asks about her glasses, "Did you have Lazik surgery?" Girl is surprised that he knows about her glasses since she only wears them in her dorm room. An awkward pause is filled with the guy changing the subject.
As she paints her toenails, ignoring him, they drive alone the open highway. An on screen clock shows they have been on the road for a couple of hours. She asks him to keep an eye out for a gas station, saying she needs a bathroom break. At the filling station, she doesn't want to get out of the car because the polish on her nails hasn't yet dried. He offers to carry her into the station, which, despite her protests, he does.
While the guy talks to the attendant, Darren Moore
, the girl finds the bathroom, which is dirty and in poor repair. After doing her business, she washes her hands only to discover the blow dryer doesn't work. After wiping her hand on her pants, she finds she cannot open the bathroom door. It is apparently locked. She begins pounding on the door for help, and though she had walked past several people in the diner section of the filling station, no one comes to help her. Eventually, she frees herself (after pulling the handle off the door). She finds the guy still chatting up the clerk behind the counter. She is furious that he didn't come to her aid. He assures her they didn't hear her cries for help, though she says she could hear them talking.
As they leave the filling station, the guy verifies his directions with the clerk, as if he is lost and doesn't know where he is going. The girl calls him on it, but he assures her he is not lost. Soon after they resume their trip, he takes a side road listed as Route 606. The snow covered road is reduced to one lane and his older car slips and slides on the packed snow. Despite her protests that they immediately turn back to the freeway, he continues saying "this is a shortcut and we will be back on the freeway in no time."
As night falls, an on-coming car approaches them at high speed in a game of chicken. They swerve to avoid it, colliding into a snow bank. A radio news report warns that an incoming storm will bring snow and temperatures down to 30 degrees below zero.
As they fight the falling temperatures, they begin to see people outside of their car, from ghostly priests to other manifestations of lost souls. Before they understand that they are spirits, the girl tries to touch one. Her hand is burned. The spirit turns to show that he, too, is a victim of fire. Bit by bit, details come out of the guy's longing for her. How he had texted her the suggestion to use the Ride Share program and posted his number for her to find. How he took the scenic route in hopes of creating a romantic memory. It also comes out that the bag she left behind was a bag of food he had bought for their trip.
They think help has arrived when a Pennsylvannia Highway Patrol Officer, Martin Donovan
, knocks on their window. Oddly, he doesn't seem to understand their predicament, choosing instead to believe they were parking. Taking the girl from the car, he tries to get her into the back of his car. When it becomes clear to her that he means her harm, she struggles to get away, but cannot. The guy appears behind the officer, welding a tire iron, and beats him across the head, rescuing her. The highway patrol officer was a spirit and the most menacing one of them all.
The spirits turn out to be spectors remaining who were victims of the rouge cop who would lure his victims to this deserted stretch of road and kill them, including four monks who witnessed his crimes. They learn of it from an article in a newspaper they are using for insulation against a car window. As the night progresses, during occassional fitful naps, the crimes of the rogue cop are re-enacted with the girl as part of them.
As the night progresses, it is revealed that the guy has sustained greater injuries from the accident than he had let on. In a desperate attempt to get help, the girl comes up with the idea of climbing a nearby telephone pole, tapping into the line with the phone from the guy's household belongings, and calling for help. While it is unclear if she is 100% successful (she makes it to the top of the pole and does make a call to 911 that is quickly lost from otherly world interference), she does make her call and returns to the car to find her travelling companion has passed away.
Defeat settles in as she tries to figure out what to do. For reasons that are not made clear, she pulls him from the car. Perhaps she is planning on dragging him to help, when a pair of headlights show up. It is a tow truck operator, Ned Bellamy
, responding to her 911 call. He loads the body of her dead friend into the back of his cab and they begin driving to safety. The tow truck driver fills in the blanks about the story of how people have been dying along that particular stretch of road since the 50's when the rouge cop was killing them. But even after he was killed, the dying continued, including people inexplicably freezing to death in the cars. It's clear this girl has narrowly escaped a very close call with death when the same car that chased her and her travelling companion off the narrow road in the first place shows up again, this time driving the tow truck driver off the road, too.
After the tow truck rolls and crashes, the girl and its driver are shaken up, but still alive. The tow truck driver insists on seeing about the other car's driver. At the bottom of a ravine, he sees a burning wreck. It is clearly the burning wreckage from the 50's of the rogue cop car. As the tow driver shimmies down into the ravine, the girl chases him, yelling for him to stop. The rogue cop is pinned inside his upside down car which is on fire. The priests show up, but rather than pull him from the wreckage, they pull the microphone for his radio from his car, preventing him from calling for help. The car becomes engulfed in flames.
The rogue cop crawls out of the burning wreckage, attacking the stunned tow truck driver. As the spirit of the cop touches the tow truck driver, he instantly freezes. The girl scrambles away, back into the damaged tow truck, attempting to start it and failing while the spirit cop reaches her and tries to attack her. That's when the spirit of her Ride Share driver appears, once more defeating the rogue cop's spirit. The girl climbs from the car, seeing the ghost of driver standing in the woods. He apologizes and says he would have explained everything to her if they had had more time. She accepts his good intentions and then follows him through the woods. They pass through the cabin where the priests/monks once lived (and died) and various other signs of the carnage created through the years by the rogue cop until they eventually reach the service station where they had stopped hours ago for fuel and a bathroom break.
Paramedics show up to treat the girl and the movie ends with her pulling up a single snapshot she took of the guy, her driver.