The Threshold & The Point of No Return
When developing characters the main patterns you will need to use are dimensions; the fatal flaw; the character arc. More advanced writers will employ even more advanced techniques like the circle of being in the back story and the peak experience as part of the subconscious internal motivation.
The Threshold Experience and the Point of no return are two additional techniques that can be used to assist character development and progress along the arc. They are also character centric demarcation point of progress alone the character arc.
The Threshold Experience &
The Point of no Return
When developing characters the main patterns you will need to use are dimensions; the fatal flaw; the character arc. More advanced writers will use the circle of being to work out the back story and where relevant, the peak experience to define the protagonists subconscious internal motivation.
The Threshold Experience and the Point of no Return are two additional techniques that should be added to the proverbial bag of tricks. I consider them advanced in the sense that they may not turn up in every screenplay. If however your work is more character based you may find these two additional plot points as useful demarcations in the character arc. You will certainly notice them in extended story lines like movie franchises or TV serials.
The Threshold Experience
This is an event or action that represents the start of concrete change in a character. It is also called crossing the threshold in the Mythical Structure Paradigm.
To have this experience the character must gain the increased awareness which the call to adventure brings about. The second prequsite is that as a result of this greater insights the character will experience doubts about change; fears of the unknown or if more experienced fear of loss. At this point the ground is ripe for a scene of crossing the threshold. In the mythical structure paradigm the optional step of meeting with the mentor can help assage these fears.
In the three act structure the antagonist will have already acteded in the the inciting incident and it is the protagonist's reaction that will thwart the nemesis plan. This reaction, the second plot marking the end of the first act can contain the threshold experience.
Alternatively some characters may be too resiliant to change or too afraid to undergo real change in this stage. In such cases the second plot point may contain action which is not be a threshold experince. In this case the threshold crossing scene can be delayed a little.
How the actual event should be formed? This experience should be a miniature or even a symbolic foreshadowing of greater changes that will enable the action of the third act climax later on.
The Point of No Return
This is usually an action or an event from which there is no going back. It can be a loss of innocence in a child, the breaking of the code of honor, a police officer who takes his first bribe. The neurotic who undergoes a psychotic breakdown. A grifter who commits murder.
The character who will later regret his action may try to return to their original state - but this will turn out to be impossible. Later they may try to change their ways, recall their honer or just do the right thing but they can never truly return. This is a major theme in Clint Eastwood's Unforgiven.
Crossing the point of no return may be portrayed either by a minor action or by a major one but either way it is a clearly demarcated crossing from white to black. It is best ported as such.