Every story needs, hold on, that's a strong word.
Let's cleanse it a little, every story (usually) requires an external event to get it going.
NOTE: This is not always true because the Protagonist's Call can be Internal as well. Keep this in mind when working on your Story Design.
It's called by many names:
- Call to Adventure (Mythology)
- Catalyst (Screenwriting)
- Inciting Incident (Screenwriting)
You're going to be overwhelmed by this term, who knows what other ones loom out there in the forest of humanity?
Just know this, the term is an external event that forces, begins, or shapes the protagonist to question and/or debate the journey.
How Myth works
In Mythology, most Journeys begin with the Hero (it's safe to use this term here), who is called to an adventure (Journey).
The Call to Adventure is an event rich with possibilities and an incredible amount of metaphoric power.
Most stories begin with the Call, but very few writers consider how the call comes.
How the call comes is just as important as how it affects the Hero.
Translating Myth to the Modern Era
Understanding the Call, you can now analyze and browse all those wonderful Myths that you enjoy over and over again.
Take some time, go back through the Myths and look deeper again.
What started the chain of events for the Hero's Journey?
When you understand this is a simple process, you're ready to wield the same power in your Story Design.
How it works in Story
Regardless of everything else, you have two options when designing your Call to Adventure.
You can start outside the Protagonist or inside the Protagonist.
If you prefer outside, then your call is a Want.
As a WANT, this is a public burden the Protagonist deals with and must change in the same manner, outside of herself.
When you work on Story Design, remember that your Protagonist's WANT is external and is solved through the PLOT (A Story, Spine, etc.).
NOTE: The problem with your Protagonist is her NEED, not her WANT. After resolving her need, she can easily resolve her want.
If you prefer inside, your call is a Need.
As a NEED, this is either a personal or private burden the Protagonist deals with and must change in the same manner, within herself.
When you work on Story Design, remember that your Protagonist's NEED is internal and is solved through the SUB-PLOT (B Story, Love Story, Heart Story, etc.).
NOTE: The problems with your Protagonist is her NEED, not her WANT. When she solves her need, she can easily resolve her want.
A Protagonist's Journey is shown to your audience in the Want Storyline, usually called the A Story or the Spine.
This is what people usually describe when they've seen a movie.
A Protagonist's Transformation is shown to your audience in the Need Storyline, usually called the B Story or the Sub-Plot.
This is what people usually describe when they talk about Theme or the Moral Premise or what the movie is "really about."