Dirty Harry local and federal police committing offences and overstepping their authority by entrapment and obstruction of justice. Author McGilligan, argued that America needed a hero, a winner at a time when the authorities were losing the battle against crime. The box-office success of "Dirty Harry" led to the production of four sequels. In the 2007 film "Zodiac", also set in San Francisco and inspired by the Zodiac Killer, cartoonist Robert Graysmith approaches police detective Dave Toschi at the cinema, where he is watching "Dirty Harry" with his wife. When Graysmith tells Toschi he is going to catch the Zodiac killer, Toschi
Dirty Harry novels of the four first "Dirty Harry" films as tie-ins. Author and screenwriter Phillip Rock wrote the novelization of "Dirty Harry" in 1971, based on an early draft of the script. Mel Valley wrote the sequel, "Magnum Force", in 1973. Wesley Morgan novelized "The Enforcer" in 1976. The "Sudden Impact" novelization was written by Joseph Stinson, one of the screenwriters. Stinson, who had rewritten the originally independent script as a "Dirty Harry" vehicle for Eastwood, adapted the novel in 1983. Following "The Enforcer", Eastwood announced that he would not make any further "Dirty Harry" films (he eventually returned to the role