The Three Act Structure

In Hollywood films the narrative tends to be organised in what is called the "Three act structure". The writer Sid Field has identified what he calls 'the ideal paradigm', three act structure. In this structure, a film must be set up within the first twenty to thirty minutes before the main character or protagonist experiences a 'plot point' that give him or her a goal that must be achieved. Half of movie running time must be taken up with the characters struggle, to achieve his or her goal: this is the 'Confrontation' period.
Sid Field also refers, sometimes to the midpoint a more subtle turning point hat happens in Act II - the confrontation which often has an apparently devastating reversal of the main characters fortune.
The final quarter of the film( the third act) depicts a climatic struggle by the protagonist to finally achieve his or her goal and the aftermath of his struggle.