This movie is kind of like the more famous 70's cult horror film "Psychic Killer" in that it deals with a prisoner who develops psychic powers which he uses to escape and take revenge on his enemies. But while in that movie the convict was an innocent man taking well-deserved revenge, the psychic killer here is a grade-A lunatic out to finish the job. In an interesting back-story he is revealed to be the disturbed illegitimate son of a famous actress/sex symbol who kept him isolated from her social circle to avoid scandal, and ended up being strangled by him. (This might have been inspired by the real-life Hollywood murder of B-movie actress Susan Cabot in the 1960's, allegedly by her troubled, illegitimate dwarf son). It's never really made clear whether his psychic "powers" actually involve astral projection(thus the alternate title "The Astral Factor") or if he is simply able to appear invisible somehow (thus "The Invisible Strangler"). The inept cops are powerless to stop him regardless, even when he is obviously in non-"astral" form and has rendered himself decidedly visible by putting on a scuba suit.
What really makes this movie though is the all-star cast(or, as some wag might say, the "all has-been and never-would-be cast"). The lead detective is played by Robert Foxworth, who appeared most memorably in the ridiculous 70's mutant bear/environmental horror flick "Prophecy". German actress Elke Sommers appears as a "special guest star" (as opposed to the other actors who were apparently "regulars"). She plays a sexy former "Miss Galaxy" who the cops try to protect while she lounges around her mansion in skimpy bikinis. Sue "Lolita" Lyon has a five minute role as an early victim without uttering a word of dialogue (which is probably for the best as acting was never her strong suit). Mariana Hill ("Mrs. Fredo Corleone" in "The Godfather Part II") appears also, in accordance with an apparent law that she had to appear in every low-budget exploitation/horror movie made in the 70's and early 80's. The best though is Stefanie "Hart to Hart" Powers, who is VERY sexy as Foxworth's bimbo girlfriend "Candy". She routinely refers to herself in the third person, and buys herself an expensive fur coat on HIS birthday (which he doesn't object to since she's obviously wearing absolutely nothing underneath it). Some will probably tune in for Powers' "nude scene" (if you don't blink you might get to see the top part of her bare butt), but frankly her whole performance is downright wood-inducing (even if, like me, you don't usually go for the whole Marilyn Monroesque dumb bimbo thing). So what, if her entire character is completely superfluous. . .
This actually seems kind of like a 70's TV movie or series episode--it would not have been out of place as an episode of "Kolchack, the Night Stalker" actually. But since I like "Kolchack" and 70's TV movies I found it pretty satisfying overall if, admittedly, not all that great.
