When a series of murders around San Francisco occur (with each victim getting a bullet in the head and one in the genitals), Harry Callahan is, to put it in a cliched manner, "on the case". Just doing so isn't an easy task, however, since his manner of investigating an unrelated case forces his superiors to force him into a vacation. And even in San Paulo, he gets trouble from the local police (led by Pat Hingle) about being the big-shot city cop.
Sondra Locke is Jennifer Spencer, an artist who is revealed early on to be the murderer of the dead men, enacting revenge on them for the gang rape of her and her sister, who is now in a catatonic state. As she kills each of the men (and a woman) one by one, in San Francisco and later San Paulo, Harry gets closer and closer to discovering the truth behind the murders as well as the rapes that led to them.
Criticism associated with this film mainly centers around Harry's principles when it came to vigilantism. In the first film, he's shown to have lost faith in the justice system he's worked so hard to help enforce. In the second, he refuses to join the group of motorcycle cops who have been murdering criminals who have escaped justice, stating that "until someone comes along with changes that make sense, I'll stick with [the system]" . While I don't have a definite opinion on this, it could look like Harry's view on this has changed between films.
Why did I think this film's probably the closest to the original in more than a few ways? Firstly, Lalo Schifrin's return to scoring the Dirty Harry movies. Though the score's updated and brought into the 80's, there are some bits of the music from the first film showing up here and there. Secondly, the issue of the justice system protecting potential suspects' rights more than enforcing the rights of victims. It's mentioned that Spencer's rape occurred ten years prior to the film, putting it sometime during 1972 or 1973, around the same time Harry was clashing with the police force over the very same problem in the first film. Finally, the scenes of the killer preparing from his/her perspective to carry out the killings are common to pretty much all the films in the series, but the amount of time spent on seeing the process is only as long as Scorpio's preparation to make his killings. And there is, of course, the immortal line "Go ahead, make my day."