When it comes to stories, the difference between a mystery and a thriller rests on the knowledge held by the audience versus the knowledge held by the protagonist. In a mystery, neither the protagonist nor the audience know the answer to the question central to the plot. The challenge is for the audience member to solve the mystery before the protagonist does. In a thriller, the protagonist doesn’t know what’s really going on, but the audience does. (See Alfred Hitchcock’s famous explanation of suspense to François Truffaut.)
My current favorite show is Dexter. It’s about a blood spatter specialist in Miami who moonlights as a serial killer (but only kills other serial killers). For the first seven episodes of the season, the show was a mystery. The main plot line of the show concerns another serial killer in Miami who is artfully killing prostitutes, and simultaneously playing an elaborate game with Dexter. We don’t know the identity of the killer, and as audience members we’re trying to work through the clues along with Dexter, the protagonist.
Last week’s episode turned the show into a thriller. Dexter has no idea who the killer is, but we now know the killer’s identity, and that one of the other main characters is in peril! So for the final four episodes of the season, the show becomes a suspense thriller. Now we hope and pray that Dexter discovers the killer’s identity before the killer can spring what we assume is his nefarious plan. Of course there are many more unanswered questions, but we’re now firmly in thriller territory.
Before this show, I hadn’t really thought much about how thrillers and mysteries differ, or about stories that transition from one genre to another. When I think about it, though, there are plenty of other shows and movies that make exactly this change. I consider it a testament to the quality of the show that it has me thinking about such things. Now I’m hoping that the writers of the show can do suspense as well as they do mystery.
If you’re not watching Dexter, you should be, but be sure to go back and start with the mystery before getting into the thriller.