Transformation from book to screenplay, Part I

In my Pima Community College's LIT 289 class we are in the process of transforming Mustang Fever into a screenplay. Here's how it goes:

Begin with AN IMAGE.
Visualization brings strong sense of place, mood, texture, sometimes the theme.
Create a metaphor for the film, telling us something about the theme.

Find the CATALYST.
After the initial images begins the story; we need to be introduced to any important characters, and information about the situation. In Mustang Fever, the intial images are dawn and we see seven wild mustangs appear out of the darkness watching Chance as he ties pilot balloons to creosote bushes, and then we see a nearby nuclear explosion out of the early dawn darkness at the Nevada Nuclear Test Site north of Las Vegas.

To start the story: the Catalyst. It begins the action of the story. In Mustang Fever, it could be Sgt. Ochs with a pick-up truck trying to drive the wild mustangs away or maybe trying to get them to run over Chance and warn him or even kill him.

This leads to THE CENTRAL QUESTION. Every story is a mystery. It asks a question in the set-up that will be answered at the climax.
In Witness, the central question is, Will John Book get the murderer? In Jaws, the central question is, Will Martin catch that killer shark? In Mustang Fever, it could be, Why does somebody want to kill Chance? And, “How do the mustangs fit into the story—what will happen to them? Will they be killed as a result of radioactive poisoning?