I won’t do this often, but this something I’ve wanted to say for a long time:
I’ve been thinking a lot about mystery plots in any type of storytelling, in particular how to write them, and I think I’ve come up with a general rule of thumb that I hope will help some people with the mystery plot line.
If you introduce a mystery right at the beginning of your story, be sure to answer it by the end of the chapter. The earlier to the start the better.
Doing this limits the potential for plot holes, which is basically a mystery that doesn’t get solved ever, or not until very late in the book–way before that point, the reader has probably put the book down. If you start with the reader getting to know your character, then you can slowly build a mystery for your story.
Granted if you do this too much, you will start to info dump. You want to pick what is absolutely necessary to the plot, at that moment in time, or that will make future scenes not contain any plot holes
Of course, curiosity and interest trumps all. That being said, not all readers have the same amount of curiosity. A five year old is going to be more curious than someone much older.