Often in a movie or a book, there is a character with a deep, dark secret. Or, there are a bunch of characters that engage in something illegal, immoral, or something of the sort. No matter what happens in the movie or book, that "secret" or that "act" will come back at a later time and bite them in the ass (for a lack of a better expression).
If the character had been involved in treason, it will come back and having serious repercussions. If the character is cheating on a spouse, he or she will definitely be caught or found out. If a character has been hiding a secret from someone for years, that secret will definitely come out in the book/movie. Of course, there are some movies where a secret is kept a secret, but it is rare and usually another secret ends up coming out anyway.
And why not? I mean, that's what makes movies and books worth watching. It is always interesting to see how the other characters deal with the issues at hand.
I think it would funny to make a movie where everyone has these secrets but none of them ever surface. One of them is cheating on his wife, and he continues to do so, whilst she is completely oblivious. The other one steals and robs regularly and is never caught. Another one has a secret identity that nobody ever finds out about. It would probably make for a very frustrating, strange, and most likely an actionless movie.
I remember a few years ago, I read the book Hotel by Arthur Hailey. There was this character who was a very intelligent, cunning, but likable crook. He stole all sorts of things, from clothes to cars to having a free hotel room for a few nights. At the end of the novel, things were getting too risky for him, and he felt he was getting to old for all this stealing and secrecy, so he decided that he wanted to live a peaceful and clean life from then on. He then grabs his suitcases and gets into his car, leaving the hotel. He stops at one point, reaches into one of his suitcases, and realizes that it is filled with twenty dollar bills; thousands of dollars in twenty dollar bills. He tells himself that this is the last dishonest thing he would do (though this time it was completely accidental), and he drives away again.
He is stopped on the road by a policeman, who was known in the police force for being "the slow one". The policeman thought he had seen something suspicious with the crook, so he looks through his car. The crook is hoping to God that he won't find the money and so are probably most of the readers. You want this crook to get away with it. Well, the policeman wasn't called "the slow one" for nothin'. He finds nothing and lets the crook continue on his way. Whew, we all breath a sigh of relief.
I thought that was great! The crook could have been caught, but he wasn't. The could-haves that usually translate into guaranteed-to-happen stays as a could-have.
Then again, I don't know how successful you can be if your movie is only full of that. The reader knows the secret of the all the characters, but they never end up coming out into the open. It may be kind of boring.
Of course, maybe that would make it more realistic and less sensational. There are some people out there who are very good at hiding their secrets and pasts.
But then again, what is more fun than creating drama? If you have a deep, dark secret, bring it out into the open, so we can have some exciting and fun drama!