Clint Eastwood first takes on the role that defined him in this violent, bar-setting police thriller.
Harry Callahan is a cop who played by his own rules before it was a cliché to do so. When a killer calling himself Scorpio begins terrorising San Francisco (Never better on film. Except perhaps for Vertigo), Callahan finds himself being forced to skirt proper police procedure in order to catch him. All this while having to deal with a new partner, the green, college educated Mexican American Chico (Reni Santoni).
The part of Harry was originally going to be played by Frank Sinatra, who thankfully had to bow out after injuring his hand. Steve McQueen, Paul Newman and John Wayne all rejected the part. Again, thankfully.
Scorpio was apparently based on a real-life murderer known as "the Zodiac Killer", who terrorised San Francisco in the 60s and was never caught.
Underappreciated director Don Siegel (Invasion of the Body Snatchers, Charley Varrick), had earlier directed Eastwood in Coogan's Bluff, and the pair later teamed-up for The Beguiled and Escape from Alcatraz.
Noted cinematic conservative John Milius (who directed Conan The Barbarian and right-wing fantasy Red Dawn) did an uncredited re-write on the film and claims to have written the classic "Did I shoot six bullets or only five" climactic scene.
Four sequels followed, of varying quality.