Every crime novel has an investigator, someone whose job it is to discover the truth. Not all investigators solve crimes, but to be an investigator you need to work hard to figure things out.
A private investigator knocks at your door. Do you let him in? He probably only wants to ask questions, because that’s what investigators do: they research. Scientists are investigators, so are police officers, and even your friend who reads lots of books about butterflies can be considered an investigator. Rooted in the Latin word vestigare, meaning “trace out,” investigators gather facts in order to trace out the whole picture.