What is the narrative structure of horror films

The most traditional way to structure a horror film is the 3 Act structure.  Signs is a good example of a 3 Act structure where the story line follows a beginning, middle and end.  Act One is the sinister beginning.  It starts with a horror teaser.  Some will start with a violent act or murder that is a shock to the audience.  Others will start with an introduction of the backstory.  It's the time to introduce the characters and setting to the storyline.  In the first act, the main character's weakness or mental insecurity can be shown and eventually used against them later on.  Next would be where the main characters meet the danger for the first time.  They now realize what they have gotten themselves into.

Act Two is the Horror Unleashed.  It starts with danger escalating and the characters start to look into researching the villain or the situation.  The characters may disappear, and some may be murdered.  A key discovery is made that changes the direction of the story.  The characters are making a plan to stop the danger or get away.  At this point, it looks like the main characters have won, but something changes to make the danger worse.  The main character prepares their final plan to avoid the danger one last time.

Act Three is the Resolution.  It is the final confrontation with the villain.  It is the scariest moment of the movie.  The character must face their biggest fear in order to survive.  The characters are either changed by the experience or die.  What a way to end!  Some films will leave the storyline incomplete to have the option for a sequel.

Another option for a horror film structure is nonlinear storytelling.  This would not follow the traditional beginning, middle, and end outline, instead it jumps around in the story by adding flashbacks or flashforwards.  By changing the events in the story timeline, it creates a more intense and emotional experience for the audience.  The introduction of the characters is more meaningful then in the traditional three act structure.  In a nonlinear structure, the storyline becomes more intense and creates a stronger sense of fear for the audience.  Donny Darko is a good example of a nonlinear storytelling where the story jumps around and confuses the audience.  The object of nonlinear create disorientation for the audience.

Tailoring the 3-Act Structure for Your Horror Film | Raindance is a good resource for the information in this blog about structure in a horror film.