Series numbering from Goodreads

"New York City: home to world-renowned museums, theater, restaurants, iconic sports franchises. Central Park. Wall Street. And an infamous serial killer who's terrorized the Big Apple for decades. The year is 1995 and the NYPD has just graduated a promising new patrol officer named Karen Vail. The rookie's first day on the job is anything but easy when she finds herself at the crime scene of a young woman murdered in an unusual manner. Vail is unsure of what she's looking at or what it means--but it's a case that will weigh on her mind for nearly twenty years. As the years pass, Vail's career takes unexpected twists and turns--as does the case that's come to be known as Hades. Now a skilled FBI profiler, will Vail be in a better position to catch the killer? Or will Hades prove to be Karen Vail's hell on earth?"--Publisher's website.