Zodiac is a 2007 suspense film about the search for a serial murderer who terrorized the San Francisco Bay area in the 1960s. Based on the Robert Graysmith book, 'Zodiac, chronicles the investigation into one of the most notoriously unsolved crimes in modern history. Filmmakers spent 18 months conducting their own investigation into the case before filming began. Early tests predicted that the movie would do exceptionally well in the box office, but it underperformed when it entered theaters. Critics have explained this disappointment by pointing out that while the film was marketed as a slasher film to younger audiences, it was, in reality, a psychological thriller that explores the intricacies of a police investigation. It has been praised for defying crime genre conventions by portraying the compulsion to solve puzzles and the realization that a final solution is often impossible.