It turns out that Sissy Spacek’s husband, Jack Fisk, had been hit by a car as a child, and she could use his experience to help herself out. “In that scene, what’s going on in my head is [Jack] walking along the side of the road when he was about 11 or 12,” Spacek explained. “It’s snowing, and he’s looking at Christmas lights. And then he saw car lights. There was a car coming down the road right at him, and it ran him over.”

It’s a surprising comparison to the shower scene, but it makes sense. Carrie’s initial deer-in-the-headlights reaction to what’s happening to her is, in hindsight, remarkably fitting. “When Carrie’s in the shower, I’m seeing those Christmas lights, and then the horror of the blood …” Spacek said. “Ain’t it bizarre that something like that could work?” 

So much of the emotional resonance of “Carrie,” both the book and the 1976 movie, is how much the tragic finale feels plausible from Carrie’s perspective. The horror isn’t just that a teenage girl murdered all her classmates; it’s that viewers and readers are made to fully believe she’s been pushed to that point. No one condones her actions at the end, but as early as that opening shower scene, we can certainly understand.