Somewhere in the first five minutes of a well-structured screenplay , someone (usually not the main character) will pose a question or make a statement (usually to the main character) that is the theme of the movie. "Be careful what you wish for," this person will say or "Pride goeth before a fall" or "Family is more important than money." It won't be this obvious, it will be conversational, an offhand remark that the main character doesn't quite get at the moment — but which will have far-reaching and meaningful impact later.

This statement is the movie's thematic premise.

In many ways a good screenplay is an argument posed by the screenwriter, the pros and cons of living a particular kind of life, or pursuing a particular goal. Is a behavior, dream, or goal worth it? Or is it false? What is more important, wealth or happiness?

One last word on the set-up as it relates to Act One. I like to think of movies as divided into three separate worlds. Most people call these three acts, I call em thesis, antithesis, and synthesis. The first IO pages and the rest of Act One is the movie's thesis; it's where we see the world as it is before the adventure starts. It is a full-fledged documentation of the hero's world labeled "before." There is a calm before the storm in this world, and especially in the set-up. If events that follow did not occur, it would pretty much stay this way. But there is a sense in the set-up that a storm's about to hit, because for things to stay as they are... is death. Things must change.

The B story gives us a breather.

Let's take Legally Blonde, for instance. The B story is Elle's relationship with the manicurist she meets in Boston. And it is a much needed break from the A story. We've met Elle. She's been dumped. She's decided to go to Law School. She gets there. And school is tough. Well, enough already, let's have a little time-out! Let's go slightly off theme here and meet someone new. Thus, the manicurist. And yes, while it is not a traditional boy-girl love story, it is in fact "the love story." It's where Elle will be nurtured. It is also the place where Elle confides what she is learning in the School of Hard Knocks she's experiencing at Harvard Law — and the place from which she'll draw the strength she needs for the final push into Act Three and ultimate victory.

The B story is also very often a brand new bunch of characters. We have not always met the B story players in the first IO pages of the screenplay. We did not even know they existed. But since Act Two is the antithesis, they are the upside down versions of those characters who inhabit the world of Act One. Again, the B story ally in Legally Blonde is a perfect example. Isn't Jennifer Goolidge, the wonderful actress who portrays manicurist Paulette Bonafonte, the funhouse mirror version of the girls from Elle's sorority house back at UCLA? This is why the character is so successful. She is a classic anti-thesis creature.

The B story then does a lot. And you must have one. It provides not only the love story and a place to openly discuss the theme of your movie, but gives the writer the vital "cutaways" from the A story. And it starts on 3O.