A plain, overweight girl hurls herself into a tunnel every day, and enters an alternate universe where a young man loves her.
Today a train catches fire and blocks the tunnel. The girl throws herself at the flaming train over and over, seriously injuring herself.. but she cannot cross.
Back at her apartment waits Michael McKean, from This Is Spinal Tap. He is a serial killer, and he has discovered her secret.
Also, he is the superintendent of her apartment building. So he has the keys.
He pulls her fridge aside and exposes the hand-drawn charts and calculations she used to enter the other world.
He grabs white paint and starts painting everything over. He is a terrible painter, and it takes forever, and is very patchy.
When the girl returns home, limping and wretched, he saws off her head.
As she dies, she realizes that the other universe only ever existed in her own mind.
That’s why Michael McKean needs her head.