The past needs to intrude into the present. Then part of the story is how the hero is trying to redeem him or herself from this past trauma.
Sometimes this past trauma occurs far in the past. In “Happy Death Day,” the hero is selfish college student who is hurt because her mother died years ago. As a result, the hero has become selfish, which is her character flaw that she needs to change over the course of the story.
Sometimes this past trauma occurs early in the story. In “Legally Blonde,” the hero gets dumped by her boyfriend just when she thinks he’s going to propose. This trauma drives her to apply to Harvard Law school in hopes of winning him back.
When plotting your own story, think of how the past can traumatize and motivate your hero. Sometimes that trauma occurs in the distant past such as in “Rocky” where we get a glimpse of his mediocre life as an enforcer for the mob, as a down and out boxer fighting in dingy gyms, and as a lonely man who pines for the affection of a girl in a pet shop.
Sometimes that trauma occurs early in the story and that’s a dramatic moment we need to witness. In “Cliffhanger,” the hero fails to save a woman who falls to her death. From that moment on, the hero is trying to redeem himself for his failure to save this woman.
If your trauma occurs in the distant past, you can show that event or simply reference it constantly. “Ready or Not” shows us a traumatic event in the opening scene, and then jumps forward 30 years later. “Die Hard” does not show us the breakup between the hero and his wife, but constantly references this problem, which creates a mystery that we want to figure out as the story progresses.
If your trauma occurs in the opening scene, we need to witness this event in all its dramatic glory. In “Kill Bill, volume 1,” the hero has been attacked by a group of assassins and gets shot in the head. Now we can clearly see the motivation she has that drives the rest of the story as she seeks revenge.
Your early scenes must not only grab the audience’s attention, but must also set up the hero’s motivation by either showing or hinting at a traumatic past event. Make this haunted past clear or mysterious and then the rest of your story will be much easier to write from that point on.