Every character arrives in your story with backstory. Backstory is what came before in their lives before the story begins. Long ago or maybe just last week, something happened that impacted your character.

In a mystery, you need to know the backstory of your sleuth and each of the suspects, including the perpetrator. If you have additional characters like a sidekick, a mentor, or a love interest, you’ll want backstory for them, too.

All of that backstory goes in your character bible. Most of it stays there.

Backstory helps you, the author, understand your character’s fears and motivations, but you don’t need to tell your reader most of the backstory information. In the same way that only 20 per cent of your research ends up in your story, only a small percentage of backstory shows up in your mystery.