Every story, in every medium, contains an arc of some kind. The journey from beginning to middle to end is the very definition of this shift. A situation and a character begin as one thing and end as another, and the middle is the path that links these two points. But in the best stories it’s not a straight line. It’s a development that builds as it goes: an arc.

One of the most challenging elements of a screenplay, and yet one of the most essential, is the character arc. Many promising screenplays begin with a good idea and interesting characters, but in the course of the story, while things may “happen,” nothing really changes.

If you break down most film plots, you will find that there is a shift in values of some kind for the protagonist. A bad man becomes good; a good man turns bad. A coward becomes a hero; a wallflower transforms into a knockout. The arc is never arbitrary. It is intrinsic to the story and it informs the action. It supports the theme and is inherent in the premise.

Character dramas are the easiest films to analyze for character arcs. For instance, in SIDEWAYS, Paul Giamatti’s character begins as an embittered self-hating and self-defeating failed writer. Through the course of the story, due to his battles with his best friend and his budding romance with Virginia Madsen’s character, he slowly regains his confidence and by the end is ready to take a risk to improve his life.

However, genre films contain arcs as well. Franchise films, such as action films, may not seem to need arcs, but in the ones that end up as classics, the protagonists do experience arcs. In the first LETHAL WEAPON, Mel Gibson’s character begins suicidal but ends up recommitted to life. In the original DIE HARD, Bruce Willis begins at odds with his estranged wife but heals his relationship with her by the end.

Some genres are practically defined by their familiar arcs. In romantic comedies, the playboy learns to commit, or the uptight career woman loosens up and finds love, or the shy protagonist gains confidence and pursues the object of his or her affection. In westerns, the misanthropic loner saves a town from the bad guys, or a weakling is forced to take a stand against the villain.

Building the character arc in your story is a matter of careful development. Scripts where a character suddenly changes or “sees the light” in the last scene ring false and are not likely to win over readers or audiences. A character transformation must be gradual, deliberate and ongoing.

In the case of comedies and dramas, where the plots essentially are character, each sequence should move the character forward in some way. One way to think of this is as “lessons learned.” For instance, in TOOTSIE, Dustin Hoffman’s character begins as a self-centered womanizer and temperamental actor. In the first act, he disguises himself as a woman in order to get a role on a soap opera, and he meets and falls for Jessica Lange, his co-star. As the plot unfolds, Hoffman gains empathy for women when the soap’s director treats him patronizingly and when finds himself stalked by the soap’s lecherous leading man. However, he also discovers that as a woman, he handles conflict better, and he is able to put his ego aside and concentrate on his craft. He gets to know Jessica Lange as a friend, not just as a potential sexual conquest, and he matures emotionally as a result. Each sequence of the movie revolves around one or more events that teach Hoffman about women, about sexism, and about himself, so that by the end of the movie, he is a changed man.

In action fare, the arc is usually prompted by a series of tests. In STAR WARS, Luke Skywalker begins as a naïve, sheltered and immature kid. The sudden and brutal deaths of his guardians thrust him out onto his own. As the plot unfolds, Luke faces one challenge after another, and each challenge contains increasing danger and higher stakes. Each test forces Luke to grow up a little, to take more responsibility for himself and his goals, and to become more self-reliant.

When you are working on your screenplay and are faced with a sequence or passage that feels emotionally empty or uninvolving, it is often because the action has become disconnected from the character. Study and analyze these troublesome passages. Is there a way in which the events of the sequence could challenge the character’s perception of himself? Would it work better to have her make a difficult, even uncharacteristic decision? Could he learn something that alters his behavior? Does her view of another character change?

Refocus the action so that it is prompted by the characters’ choices and growth. This will make your characters more than just props in the plot and also make them more appealing to actors. In addition, it will result in a more emotionally involving story -- one that is more likely to engage readers and later your audience.