The Ripper Letter

Ancient codes and a legendary killer lure a young detective into a dark and dangerous world. When a murdered historian is marked with a mysterious code, homicide detective Dee Brentano worries about his colleague - her missing father, Alexandre. FBI special agent J. R. Pierce tells her that Alexandre is wanted for this murder. Desperate to find him first, she discovers that Alexandre has items that several people - including Pierce - would kill to possess.
One is a letter attributed to Jack the Ripper. Another is an erotic cryptograph. Dee encounters a potential ally in Detective Gregory Brenner. She's attracted to him, but fears that he's playing her to find her father. She's also drawn to her father's protégé, Scott Bateman, who can decode the Ripper letter's secret message and the symbol on the murdered historian. It's bait for luring supernatural entities.
It's also a map to locating her father. Dee must choose her path wisely. One leads to a supernatural lover, the other to an immortal serial killer. Dean Koontz called Ramsland's Ghost: Investigating the Other Side, "The best book of its kind I've ever read, " and Publisher's Weekly stated that "Ramsland is a master of foreboding." Whitley Streiber found The Heat Seekers to be a "gem" and said, "Katherine Ramsland is a marvelous novelist, who approaches her subject with chilling, fascinating inner knowledge."