I was always interested in the case of Dorothy Kilgallen, a well known investigative journalist at the time (Had her column in over 200 newspapers). She was the only person who had interviewed Jack Ruby, twice I believe.
She was highly influential, and was friendly with JFK and upper-class New York society (For example she had a friendship and feud with Frank Sinatra). She was a daily panelist on the hit TV show at the time "What's my Line", and was known for her celebrity-attended parties. She was on the show live, hours before her death. Be aware there is tons of hearsay when this is discussed, but it is still fascinating.
She went full force into the JFK investigation, not believing Oswald acted alone, publicly stating that in her column. She allegedly carried a file around with her at all times, and told her close friend she was "going to release the largest story of the century, and blow the entire JFK case sky-high". Eventually she expressed fear for her life to her closest friends, became more paranoid and had bought a gun, which was out of her character. When in New Orleans investigating a contact, she had apparently told her assistant to go back to NYC and tell no one, in a frantic panic.
She was soon to submit her findings, but in 1965 she was found dead after having an affair with a much younger man who came out of nowhere. Her files were missing, and she was found by her hairdresser in a bedroom she never slept in, with clothes she would never wear to bed, reading a book she had finished and disliked, wearing glasses when she didn't need them for reading. Her case was closed as barbiturates and alcohol. NYC actually reopened an investigation into her death in 2016 due to a book published recently, but closed it in September this year with no evidence of foul play.
I looked up her name out of curiosity, and there appears to be an entire file named "DOROTHY KILGALLEN", by Richard Nixon, it appears to still be classified for reasons of national security…
In another declassified document it just reads at the end "She has no idea as to how DOROTHY KILGALLEN came into possession of a copy of the deposition"
EDIT 1 UNVERIFIED: But I remember reading that after her death, when asked about the file she carried around and where it was, her husband replied "That will have to go to the grave with me". Her TV co-stars, including Benett Cerf, founder of RandomHouse publishing (was to publish her JFK book) all shut their mouths. Allegedly her co-star Arlene Francis was afraid she knew too much from their daily conversations (she lived to 91, so take that as you will).
EDIT 2: Found in Jim Garrison, Lead File 1a. Randomly when searching. Apparently a hotel owner, Mrs. Jackson said that a Robert Ahler had stayed in her hotel for 3 weeks, and she thinks she had seen him with a familiar face (Oswald) and left communist propaganda in one of the drawers, as well as a swastika.
Underlined by whoever did the investigation, was that he spent $2o a week on phone calls to New Orleans….interesting.