Except for victim names, this true-life story of the infamous serial killings in Los Angeles in the late 1970s is mostly factual, and is told from the POV of the two killers: Kenneth Bianchi (C. Thomas Howell) and Angelo Buono (Nicholas Turturro). As such, the film functions largely as a character study of these two criminals. The script is structured as a series of events, in chronological order, beginning with Bianchi's life in upstate New York, where he started out as a petty thief.
Although he apparently tried to live a reasonably normal life, Bianchi felt constantly rejected, especially in his repeated, unsuccessful efforts to join the police force. He tells his mom: "Whatever I do, nothing ever turns out right; sometimes I just want to find some tall building and take a big fall".
His hook-up with Angelo Buono in Los Angeles proves fatal. Buono, a domineering, unctuous brute who haunts the tawdry, seedy areas of LA, persuades Bianchi to go into the hooker business. But that effort backfires as a result of one particular prostitute and as a result, the two men lose their "business". Seeking "payback", they lure into their presence, and then kill, a whole series of women, mostly street hookers, as a way to "settle the score".
Their murder partnership calls to mind the symbiotic relationship between Perry Smith and Dick Hickock, in the film "In Cold Blood" (1967). It was the liaison, the merger of mindsets that ultimately led to the killings.
Some of the scenes in "The Hillside Strangler" are quite graphic. They are hard to watch because the victims are portrayed as real people who happened to be at the wrong place at the wrong time. I think the Director could have spent less time showing us the nude bodies of the victims, which strikes me as gratuitous and unnecessary.
Both C. Thomas Howell and Nicholas Turturro give performances that are credible. Allison Lange, as Bianchi's girlfriend in LA, provides about the only semblance of humanity in this dark story. Toward the film's end, an effort to enact a copycat killing renders an interestingly strange plot twist that presumably really happened.
The entire story is very depressing and disturbing. However, visual shock value notwithstanding, the film's presentation of that story is realistic and credible. It's not for the faint of heart. And the film's story has greater breadth than depth. But as a general overview of events and of the mindset of the two criminals, "The Hillside Strangler" is certainly worth watching.