Hello, need help with a plot twist.

Hello from Mexico.
I've been working on a screenplay for about 2 weeks now. I'm almost finished with it, and I've got many endings in mind, but I would like to end the screenplay with a big surprise, something completely unexpected, yet coherent (AKA plot twist).
A little about the screenplay: It's about a Detective who somehow finds out a journalist who writes only about murders is somehow responsible for the murders he writes about. The final scene is a conversation between the Detective and the journalist. As I said, I've thought some endings up, but since it's kind of a thriller, I'd like to end it with a plot twist. The plot twist could be about.
-A relationship between the victims;
-The real reason why the journalist does what he does (not only for money);
-Or a revelation from the Detective, a change of positions. You know, like the Detective turns out to be the bad guy and the journalist the good guy.
Thank you for your help in advance. If you have any questions about the screenplay (I tried to be as concise as possible), feel free to send me a private message.
 
A good plot twist comes organically from the story. It needs to be set up
and followed through several times in order for it to be a successful "twist".
Of the three you mention each one can work depending on what you have
set up in your story.

- Is there a relationship between the victims? Have you set up and reinforced
that in your story?
- Have you set up and reinforced the real reason why the journalist does what
he does so when it's revealed the audience should have seen it coming?
- In your story have you set up and reinforced that your protagonist is actually
the antagonist?

Have you done all three? Is that why any of these three can happen? Or you
hoping you can just throw in a twist and it will work?
 
Back
Top