Mystery  is something full of unexpected things and unusual experiences which creates a un believable thing in your life. which makes u turn back and see it every-time. at starting u will not what is happening  around u and as go deeper and deeper u will understand all the thing' it  will make u believe in fantacy. it might be a theft ,murder or crime. it is a document full of surprises 
and unbelivebal things one cant belive without experiencing them. anyone can go through a mystery  at any age. it might be a fiction  or bitter experience or negative or positve.