What mystery in your own life could be a plot for a book?
Well, it's funny you should mention that! Mystery and me seem to have a thing going; there have been lots of mysteries in my life, or rather in the lives of family members, which is maybe why I'm repeatedly drawn to mystery as a subject matter and genre for most of my writing, and yes, the plot of one of my books IS a family mystery!
Both of my parents hail from Northern Ireland, and I lived in Belfast as a child during the Troubles; many unanswered questions haunt our family and friends, including the reasons and the perpetrators of several crimes of violence. One of my books-in-progress (And the Buntings Flew) deals with a specific shocking event during the Troubles and reimagines this historical mystery from the perspective of the wider community.
Maybe not in my own life, but mysteries fascinate me; I have just published a novella (https://www.amazon.co.uk/Battle-Watli...) that takes a very alternative look back at the mystery of what happened to Queen Boudicca, after her defeat by the Romans in AD61.
I'm also writing a follow-up novel, a Science fiction story that brings the mystery into the current day, and again is based on several unexplained phenomena in my life. Nothing very earth shattering (that's a clue!) but aren't those little niggling questions sometimes the most profound mysteries that we struggle with?