One thing my agent is always hounding me to do is make my story ideas "more," to really go for a strong conflict and a big idea that will make the story stand out. Based on responses I've seen to her blog posts about this and the questions we get when we do workshops together, and based on some manuscripts I've judged or critiqued, I get the impression that there's some confusion about how that works. What often results is what I'd call "kitchen sink" writing, where the author throws in lots of stuff (everything but the kitchen sink) to try to elevate the story, but the result is something more scattered.
On a recent Sunday afternoon with HBO I ran across a movie that perfectly illustrates kitchen sink writing. (And incidentally, I tend to use TV and movies as examples because, with the possible exception of mega bestsellers, more people see even the worst-performing TV shows and movies than read even the best-performing books, so the chances that you've seen the TV shows or movies I'm referring to are much greater than that you've read a particular book.) The movie was The Family Stone, and I found it very frustrating to watch because there was enough material to fill several films, yet none of these story lines were as fully developed as they should have been, and a lot of the stories didn't really relate to each other. The impression I had was that either the writers or some studio exec didn't have faith in their central story, so they started throwing in more and more plot elements.
There was the main plot of the man bringing his girlfriend home for the holidays to meet his large, close-knit family, and they all immediately hate her -- except for one of his brothers, who likes her a bit too much.
There's a related subplot in which the girlfriend feels threatened and outnumbered, so she calls in her sister for moral support -- and the sister turns out to be perfect for the boyfriend, which created some dilemmas for everyone.
That alone seems like it could have been a strong enough conflict to carry a story, but the writers also threw in:
The bitter, antagonistic, single sister who leads the campaign against the girlfriend and who seems to be something of an underachiever or at least possibly feels threatened by the girlfriend due to her relative lack of success (something they seemed to be pointing out with the visual of her arrival in an old, junky car), and who wants to avoid her former boyfriend while she's back home, even though he's been asking after her (and we never really learn what the deal was with that, since she pretty much fell right into his arms when they did see each other).
The mother who has learned she's dying of cancer, and who wants to have one last family Christmas before she tells her children about her illness.
The pregnant sister whose husband hasn't managed to make it home yet (I was never sure if that was meant to be a sign of a possible problem in their marriage with him being too busy for his family. It seemed ominous, but then nothing came of it.).
The deaf, gay brother and his black partner who are trying to adopt a child. (Which had absolutely nothing to do with the main story. I guess they were trying to check off all the politically correct demographic boxes with an interracial gay couple with a disability, or else they managed to hit the trifecta of Magically Insightful character types (gay, disabled, black), or maybe they were ripping off Four Weddings and a Funeral with the insightful deaf younger brother and the gay couple that's more sane than any of the other couples).
There seemed to be some hints that there was a story behind the brother who liked the girlfriend, based on remarks made about him when he arrived, but this was never really explored.
Each of these subplots had the potential to be its own movie, but their inclusion in this movie didn't add to it. They mostly served to eat up screen time that kept them from fully developing the main plot and the subplots. You could remove all of them without much affecting the main plot (I guess you'd still need the antagonistic sister to create the tension in the main plot, but she didn't need a subplot about her ex-boyfriend), and you could build an entire story around each of these subplots without even touching upon the main plot.
To better develop that main plot, you'd want to look into why the girlfriend was so brittle and what her "freak flag" that the brother claimed to see was all about. You'd want to know why the boyfriend was with her in the first place and why he was willing to stand up to his family on her behalf -- but then be able to fall hard and fast for her sister. You'd want to know why the brother liked the girlfriend, and what his issues were (he seemed to be the black sheep of the family). You'd think there would be a lot of internal conflict in the idea of realizing that the perfect person for you is the sibling of the person you're dating (or is dating your sibling). That's a huge dilemma that seemed to be glossed over entirely in this movie and resolved far too easily. And there's external conflict in how this would affect the family once it all comes out in the open. You'd also need to explain why the family would hate the woman for one brother but then totally accept her with another brother. Not to mention the fact that you'd need to make up your mind about the girlfriend character and decide if she's truly so awful and selfish with offensive opinions, or if she's the victim of a family not keen on outsiders, and her nerves caused most of her problems. Even by the end of the movie, I still wasn't sure if I was supposed to be sympathetic toward her, and that lack of focus with one of the main characters is a key symptom or result of kitchen sink writing.
Depending on your answers to these questions, you'd be able to come up with a story pitch that sounds a lot stronger and that demonstrates some of the conflict.
For a contrast, the TV series Pushing Daisies has a lot of stuff going on, but it all manages to tie into the central premise. Theoretically, a TV series should be at a disadvantage against a movie in this respect because a movie has to deal with all its plots and themes at one go, while a TV series can go episode by episode, but Pushing Daisies is far more coherent than The Family Stone (and by that I mean it holds together rather than that it makes sense, since I'm not sure it does, and I mean that in a good way).
The central idea behind Pushing Daisies is that Ned has an odd talent that allows him to bring any dead thing back to life with a touch, but if he touches it again, it dies for good, and if he doesn't touch it again within a minute, something else nearby will die. In other words, this guy has the power over life and death, but in a restrictive, inconvenient way. That's your high concept.
To add more conflict and action to that, a PI who finds out about this talent partners with Ned to solve cases of mysterious deaths -- bring dead people back for long enough to find out how they died, make them dead for good, solve the case, collect the reward. This plot couldn't exist without that main plot.
For internal conflict, there are Ned's emotional issues relating to his talent and how it's affected his life, leaving him closed off and afraid of human contact. Again, this wouldn't be there if not for that main plot.
To add some romance, one of the murder cases he investigates turns out to involve his childhood sweetheart, and he can't bring himself to make her die for good, so he keeps her alive. Now he's around the woman he loves, but he can never touch her. That ties to the main plot, the primary story plot and even involves the internal conflict.
Her story involves the aunts who brought her up after her father's death (which was inadvertently caused by Ned reviving his mother when she died, before he understood how his talent worked) who now think she's dead, and she can't let them know she's alive. This situation wouldn't exist without the main plot and the PI plot, and it also has something to do with Ned's emotional issues, which could threaten the romance.
And we've also got some external conflict for the romance (beyond even the no-touching issue) in the form of the waitress who's been pining over Ned, who's not happy to see his childhood sweetheart come back, and through becoming friends with the aunts, she starts to think the sweetheart faked her own death and wants to use this information to gain favor with Ned. This isn't necessarily directly related to the main concept, but it ties to almost all of the other subplots.
Every one of these plot lines increases the problems and tension relating to that main plot, and if you remove any one of the subplots, most of the others would come crashing down because it's all so intricately woven together.
When you feel like you need to strengthen or deepen the conflict in your story or raise the stakes, before you're tempted to throw in the entire Sears housewares department, look at your main plot to see what could make it better. What's the worst thing that could happen to your main character within the context of your main plot? How could you make that happen? How could you make matters worse for your main character? What's the possible result if your main character doesn't achieve his goal within the main plot? How can you make that seem even more dire? If you're adding subplots to complicate the main character's life (much as they've done in the Pushing Daisies example), ask yourself how each subplot relates to the main plot to make it that much harder for the main character to achieve his story goals, and see how tightly you can weave together the subplots so they all affect each other.
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