User blog comment:Zathronas/Author's Advice: The Art of the Mystery/@comment-6830001-20140205005136

That's necessary points indeed. I think one of the most unexpected main plot's answer I read was in Le Mystère de la chambre jaune (I don't know the english title though) by Gaston Leroux. It was simple but unexpected...

I'm always impressed by writers who come up with numerous great mystery stories, very famous like Christie or Conan Doyle or less famous. For example, Gosho Aoyama who publishes weekly the manga Detective Conan since 20 or 25 years and always comes up with different secondary mysteries while making the main plot progress slowly bit by bit...

I guess you could maybe add the character who will solve the mystery. It won't always be the main character (if the main plot of the mystery is only a part of the story)...