A few years ago, after watching one too many whodunnit TV mysterys, I coined my
- Law of Economy of Characters
- The killer is innocuously introduced in the first 20 minutes
In real life, the killer may not be known until late in the investigation—if ever.
In a TV mystery, any non-recurring character who gets more than a few lines has to be a potential suspect—to the audience. The character is not there gratuitously. Their salary is being paid for a reason.
It’s not universally true, but it works more often than not. It’s less true in books, where throwaway characters are easy to introduce.
Googling around, I found the following, attributed to Roger Ebert:
- Ebert’s Law of Conservation of Characters
- Any main character whose purpose is not readily apparent must be more important than he or she seems
I’m in good company.