I came across this movie in a list of movies inspired by true crime cases. The inspiration for this film was the cases of Ted Bundy and Edmund Kempler.
The script is very simple, clearly having some influence by European films like 'Bird With The Crystal Plumage' or 'Black Belly of the Tarantula'. However, Maralyn Thoma doesn't make this mystery that complex, focusing more on the cat and mouse game between the killer and the detective.
Compared to most modern slick thrillers and horror movies, it is easy to consider this film dull with it's steady progression and lack of cheap fake scares. What this film is trying to achieve isn't cheap shocks but a slow sense of frustration and dread.
The killer is underdeveloped as a character for a simple reason, this film is from 1978. A lot of the information about serial killers, their psycho-pathology and victimology was still being developed at the time. Without the information we take for granted now, it was much better to keep the tension by detaching from the killer, making him a monster by mystery.
The actors in this film are giving their all. James Luisi is a very sympathetic, complicated protagonist, absorbed in this case and torn between his home life with his family, and his mistress, a psychologist who can give him his first clues on the nature of this kind of monster.
The girls playing the victims are very convincing in their naivety, their shock at being trapped and their fear being in the hands of a madman. They aren't mere cookie cut bodies or subtly being blamed for their victimization, with small action and dialog, they are made real and ordinary for us.
Oh, and also because it is a late seventies film, there has to be one lame, over sentimental song. That's just a given.
This is an overlooked film, and that's a pity. For a true horror maven, it is well worth watching.
