Unsolved Mysteries

I was asked an author question on Goodreads. Is there an unsolved mystery in your life that would make a good plot for a movie? This was my answer:

A close relative (who passed away a long time ago) was accused of a horrific crime many, many years ago. I was a child at the time and had no idea what was going on. It was only later in life that I learned anything about it. Long story short he was cleared of all suspicion, because he was completely and totally innocent, but apparently the experience really shook him up, understandably. Goes to show that sometimes you only have to be in the wrong place at the wrong time. The mystery part is, who really was the guilty party? I don't know if anyone was ever arrested or not. Did they get away with it? How? And why did they do it in the first place? Hmm, interesting...

What about you? Got any unsolved mysteries that would make a great book? Do you think you will ever write it?