The 70s churned out a lot of films like this one. There's The Manitou, The Sentinel, The Prophecy, etc. All bear a resemblance in that they could have been classics of the genre but instead fall a little too far into the realm of hokum. That's not to say that I didn't enjoy all of them. They just aren't really all that good is all.
Based on a novel by Graham Masterson, The Manitou is about a woman who believes that she has a tumor growing on her neck. When she goes into the hospital to have it removed, they discover that it is in fact a fetus and that it is growing. I really can't say how close any of this is to the source novel as I haven't read it.
Tony Curtis plays the ex of the young woman. He's a charlatan psychic who finds himself up against a real supernatural threat. Susan Strasberg is the woman with the growth and Burgess Meredith pops up as a professor who knows about the legend of the manitou.
The whole thing is rooted in native American legend. A manitou is a spirit that can be born on a man, woman or animal. A manitou can also be reborn many times until it reaches a level of rebirth and is accepted by the spirits as one of them. Don't quote me on that, I may have it wrong but it goes something like that.
The acting is passable, with no real standouts in the cast. The writing again is passable. The special makeup effects are impressive when they do show up. What really stands out for me in the film is the vertically challenged Indian who emerges from Strasberg's back. He is creepier than hell and used to good effect as the titular villain.
So here it is: The Manitou is a film that could have been really good and stood the test of time. As it is, it remains a solid flick, but completely forgettable.
