context: It's 1958 in Detroit. We are inside a car factory where numerous Plymouth Fury's are being assembled. Among the rather plain-colored vehicles, one of them stands out: a bright-red one. During the process, this particular red car is being fussed about by one factory worker who has his hand injured when the vehicle's hood comes down on it. Another factory worker takes a seat inside the vehicle; he will be found dead afterwords.Present day, September 16, 1978 in Northern California. Arnie Cunningham (Keith Gordon) is a meek teenager who spends his weekends playing Scrabble with his parents (Christine Belford and Richard Darnell), who still treat him as a child. Arnie and his best friend Dennis Guilder (John Stockwell) are going to their school, as usual. Arnie is clumsy, and his black-rimmed glasses characterize him as being nerdy. Dennis is a football player, who still befriends Arnie and tries to stand up for him.During shop class, Arnie is bullied by several students led by Buddy Repperton (William Ostrander). Dennis tries to stop the bullies, but he can't be all the time checking on weak Arnie. Today, Buddy stamps on Arnie's sack-lunch and also breaks his glasses. When both Arnie and Dennis tell the shop teacher that Buddy had a switchblade in his possession when he teased Arnie, it looks that the only consequence will be bad for Arnie, as Boddy announces he will take his own back pretty soon.Arnie and Dennis start their way back to their homes. Arnie notices a used Plymouth Fury with a placard announcing "SOLD". Supposedly, this is the same vehicle that we saw on the Detroit assembly line... only now it's dirty, gritty, broken, with pieces peeling off or falling apart. In spite of everything, Arnie falls in love with this car. He immediately wants to buy it. The owner, George LeBay, tells the story of the car: he inherited it from his dead brother, Roland. The current owner also tells Arnie that the car has a name: Christine.Arnie drives Dennis home in his new car. Once at home, Arnie's overprotective parents angrily start pestering him for having spent his money on a car without consulting them, and especially one in Christine's wrecked condition. Arnie angrily shouts back that throughout his life, they haven't allowed him to have something he truly wants, and that he is dead-set on keeping Christine. However, his parents refuse to have it parked in their driveway. Arnie decides to take it to a local junkyard garage run by an irritable middle-aged man named Will Darnell (Robert Prosky) for storage.Over the next several weeks, Arnie begins working on Christine whenever he has a bit of free time after school. He also starts to help Mr. Darnell around his garage. This was the first time when Arnie stood up to his parents. However, it's not only about being against parental control. Dennis also notices a subtle change in Arnie, as he seems to be more assertive. Weirdly enough, Arnie has stopped using his eye glasses.During a football game, Dennis is shocked to see Arnie arrive in Christine, now fully-restored into a shining beautiful red car, but also along for the ride is the new student, Leigh Cabot (Alexandra Paul). The sight of the two of them together causes Dennis to make a mistake on the field as he's tackled hard. This puts an end to Dennis' football career - and to his ambitions for the future-, so he ends up recuperating in hospital, surrounded by medical paraphernalia.Meanwhile, Arnie continues to date Leigh. One night, he takes her to see a film at the drive-in; and there, Leigh confesses to Arnie that she thinks he's moving too fast in their relationship. She also claims she feels unsettled when she is around Christine. During the movie, one of Christine's windshield wipers becomes stuck, and Arnie gets out to fix it. As he does so, Leigh chokes on a hamburger and immediately, the door latches lock themselves! Arnie tries to get back into the car unsuccessfully. Basically, Leigh has to save herself when she manages to unlock the passenger door, and a nearby viewer who saw her struggling performs the Heimlich maneuver on her.Arnie then drives Leigh home. At her doorstep, she tells him that she won't go anywhere in Christine again. There are weird things about the car, she says, like when only old songs can be reached through the radio aerial, but none of the local radio stations can be heard. Arnie then returns Christine to Darnell's garage.After Arnie's departure, Buddy Repperton and his thugs arrive, and they proceed to systematically destroy the car. Arnie sees the wreck done to Christine the following day and is shocked that all the work he had put into restoring the car has evaporated.Arnie suspects that Leigh was somehow responsible for the wreck. He is getting into trouble as home as well, as his temper is radically changed. His parents notice the acute change in him and they comment that they want the old Arnie to come back. The long Scrabble nights are over, and Arnie has one big row with his father. But more and more, Arnie can only think of one matter: he wants to restore Christine to its full beauty again.Next day, first thing he does is going to the salvage garage to re-start work on Christine. Determined, he looks for his tools. Turning his back on Christine, he hears the crinkling of metal behind him. Arnie looks at Christine startled, and he realizes that, part of her engine is now repaired as if by magic. Arnie doesn't look startled anymore, and he encourages Christine to restore herself in front of him. The car flicks her headlights on, and obediently, there is suddenly mayhem: pieces are moving to their original position, the hood dusts itself off, the aerial strengthens up, buttons and seats start mending themselves and end up being shiny as brand new. The living malevolent car has the power to regenerate.A more-determined Arnie goes back to high school life. Nobody dares to touch him now. At night, Christine comes to life by herself and she seeks out and gruesomely kills each gang member who took part in destroying her. He runs after them. Eventually, Christine arrives at a gas station, spilling gasoline, setting it on fire so that the building becomes debris and ashes. Christine catches fire herself, but that doesn't stop her, as she still goes after Buddy. He tries to run away the scene, terrified because he has seen an unexplainable thing happened. The following morning, Chrisitne becomes the quiet, shiny, brand-new red car of the cover painting.Christine also kills grumply Will Darnell, by the slow method of crushing him in the front seat against the steering wheel. Christine has to deform herself in order to do this, but the following morning, she is in perfect condition.Some weeks later in December, Dennis catches Leigh in high school between classes and he talks to her about Arnie and his car. Dennis and Arnie are not best pals anymore, and Leigh had realised that, in spite of not having broken up verbally with Arnie, there is no place in his life for her. Holidays approach, and New Year's Eve is close. Dennis and Leigh talk about the supernatural element in Christine, knowing that they can only talk to each other about that, as nobody else would believe them. They know they will have to kill Christine.Dennis decides to call on his old buddy at his home, but Leigh advises him to take caution. After she leaves, it's Arnie who calls on Dennis instead. Arnie arrives in Christine and invites Dennis over. Arnie drives Dennis to the former's. Dennis realises about Arnie's dazzled eyes, even before Arnie starts doing things he would have never done before, during his nerd phase: he drinks beer in Homer Simpson-quantities, he terrorizes other drivers and even copies the "without-hands" motorbike stunt. Dennis watches how Christine's mile counter moves backwards, having less miles instead of more. Arnie tires to explain to Dennis how wonderful, strong and fulfilled he feels when he is driving Christine; Arnie's words increasingly become those of a starry-eyed lover.When Dennis leaves Christine, he is more unsettled than ever. Dennis is determined that the nightmare has to stop. He thinks that killing Christine is the only way of returning Arnie to normal. Dennis and Leigh may be having a thing going on between them, but it also may be that each one is the only safe rock of the other. They are worried about Arnie, especially Dennis, who really misses his best friend. Next morning, Dennis goes to the school parking lot and scratches "Darnell's Tonight" into Christine's hood, and drives off with Leigh. They go to Darnell's scrapyard and they wait for Arnie and Christine inside a bulldozer. Night falls down, and Dennis devises a plan. He tells Leigh to wait in the office. The plan is that she will shut door on Christine after her arrival, trapping the vehicle inside the office.Leigh leaves to do so. While she is on her way there, the car's lights suddenly break the night: she was hiding under a pile of garbage. Christine drives towards Leigh trying to run over her, but crashes on to one of the office walls instead. Arnie gets ejected through Christine's windshield and is impaled on a shard of glass, fatally wounding him. Arnie is bloodied, but in his last breath, he just caresses Christine's front bumper for the last time. In his own way, he dies happy.Enraged, Christine attacks Leigh once again. Dennis drives the bulldozer and he fights Christine, who is playing  Pledging My Love  at top volume on her radio. Christine is still set on dealing with Leigh first, so she approaches her top speed to run over her. However, Dennis drives the bulldozer up on to the car's back, stopping her and crashing her. Leigh climbs in to the cab of the bulldozer and embraces Dennis. Meanwhile, Christine returns back to life and begins to heal herself over again. So, Dennis has to drive the bulldozer over Christine, crashing her onto a thin layer of metal and glass materials, until her headlights flicker and then go out for good. Dennis compacts the red car onto a cube.The ordeal is over.However, later on, within that scrape-yard cube, a metallic stick starts to slowly move and straighten up...
question: Why does Christine crash into Darnell's office ?
answer: Trying to run over Leigh