Long story short: I'm writing a noir-ish sci-fi murder mystery. Thing. Sort of. Anyway, I've got a private detective as my protagonist, and my knowledge and exposure to private detectives is pretty much limited to Sherlock Holmes and Humphrey Bogart. Obviously, I'm checking out books from the local library, and doing whatever research I can, but I could use a few pointers. Questions I have: A) What can the PI do? More specifically: How does a PI generally interact with the police on a case, where can a PI go that the police can't, etc. Is it realistic, for example, for a PI to have a prison guard as a contact, who can let him in to the county jail to talk to a suspect? Is it realistic for a PI to call up a bookstore and get access to surveillance tapes? Would the PI's testimony about the tapes be admissible in court? Can a PI interview witnesses to a crime, or would he have to go through an attorney? B) How realistic should I make the PI? Should I interview real PIs to see how they operate? In short, how much research should I do to ensure realism and accuracy in my portrayal of the profession? The thing that's making me a bit stuck is that this isn't like "The Big Sleep," where there are a bunch of people engaged in a conspiracy that Bogie is trying to uncover. The crux of the mystery lies in something that none of the characters has any control over, or is really aware of, and yet that uncontrollable thing is what causes the original murder to happen in the first place. I can't figure out how to get my detective from point A, being hired by the victim's widow to prove the innocence of a wrongly-imprisoned suspect, to B, discovering the uncontrollable thing that is not at all evidenced at point A. It's complicated, to say the least. Any guidance would be appreciated.