Theory: Syd Field's Narrative Paradigm

Syd Field was a writer. He devised a paradigm (scheme) which helps the narrative structure flow and stay together. Field states that almost every film can be divided into 3 acts, which encompass different parts:

Act I - In 2 hour long movie, this act lasts approximately 30 minutes
Setup - the scene is set here for the rest of the movie. It is usually where everything is "normal".

Act II - In 2 hour long movie, this act lasts approximately 60 minutes
Confrontation - the audience  are presented with a situation/issue that must be overcome by the characters.

Act III - In 2 hour long movie, this act lasts approximately 30 minutes
Resolution - the situation/issue is overcome and everything usually returns to "normal". The ending is reached.

Field also says that there are two "pot points", which push the plot in a new direction. They lead to a new act. Other writers have substantiated Field's work by saying that the first plot point is when the protagonist confronts the issue.

A visual demonstration of Field's theory

Image Source: dramatica.com