This book chronicles the history of the self-named Zodiac Killer who was active in the 1960s and 1970s in
California from first hand details covered by Graysmith's investigative efforts to unmask the Zodiac. The book describes the investigations of the many law enforcement branches such as the
LAPD, the
FBI, the
CIA, etc., that worked on the case and other murders that the Zodiac had proclaimed he committed, including the 1966 Cheri Jo Bates stabbing. Later chapters deal with Graysmith's many theories on the case, and the book eventually cites two possible suspects (who are given pseudonyms), Bob Starr and Donald Andrews, and details some of the circumstantial evidence against them. Graysmith received assistance from
police departments that fell within the jurisdictions of the murders, and especially from Inspector
Dave Toschi from the
San Francisco Police Department, who had worked the Zodiac case. Although the case was never solved, there were instances where solid evidence was held among a number of suspects, even after the Zodiac murders had stopped. ==Background==