File under, “Lessons learned while writing.” I have a tendency to throw details into a story that explain a problem in my head, but are not meant to go further than that. But a reader, who is not in my head, reads that detail as crucial, and chases it down the rabbit hole until they realize it is just a dead end. Frustrating. And no tiny doors to climb through at the bottom.
For example. A new character shows up out of the blue, and announces that he is here to investigate an old death that he believes is murder most foul. Murder? How unexpected! How juicy! Who died, and why? Who is this murder investigator? Tell me more!
But the investigator is really here for some other reason. He made up the murder investigation as a cover. I move on with his real motivation, and ignore the murder, because, what murder? Boring!
But the reader is intrigued, then confused, then lost, then maybe disappointed and angry. And when they emerge from the other end of the stages of grief, they have missed all the good stuff I was doing in the meantime.
Must avoid the unintended red herring.