It's my turn to talk about writing in the dark, and for me the best part about "dark" mysteries and novels is the suspense that provides the primary conflict in the story. For me dark, isn't necessarily about brooding, atmospheric prose, or scary, edge of your seat concepts, although both fit nicely into dark stories. For me, dark is the willingness to push characters to their breaking points and beyond. It's all about torturing your characters with obstacles, failures, dead ends and resolution of questions that lead to bigger, more dangerous stakes.
I hate to say this, but torturing characters is fun.
Here are some dark ideas you might use to torture your characters (and keep readers turning the page):
Life or death stakes: These can be physical or emotional, literal or symbolic. Make the outcome of the story matter to your character in a profound and personal way.
Secrets and lies: Miscues, wrong assumptions, deeply buried secrets that change everything. Readers love to be surprised, so make sure your characters are flawed, harbor secrets and jump to wrong conclusions. Now figure out the worst possible time for their secret to be discovered, and make it happen.
Villains with a reason: A great villain doesn't think he's the villain. He thinks he's in the right. Give your villains a justification for their actions, make them righteous and multi-dimensional. We love tortured souls.
Consequences: Make sure that your characters' decisions have consequences, don't let them take a step forward without taking a step back, or sideways, or somehow raising the stakes. Every action, every decision, must have consequences.
Betrayal: I hate (love) when a character's motives are not what I had originally assumed or a character that is forced to turn against her beliefs. Nothing adds tension to a manuscript like good old fashioned betrayal.
Comedy: Okay, this one is more to relieve tension, but you have to let the reader take a breath now and then. I think the best dark stories include moments of levity. A little dark humor goes a long way.
No win scenarios: Nothing increases the stakes like a no win situation. Give your character two bad choices and no other way out.
Worst case scenario: What's the worst thing that could happen to your main character? Make it happen! Sooner is better.
How do you torture your characters?