The rest of the cast (save for Shelly Winters who I've never liked, thankfully she's only in a few scenes) is good too with Lance Henriksen in an early role as a bad guy and the kid playing the little girl is rather awesome in a way. At one point she "innocently" cripples her mother at her birthday party with an errant gunshot (I'd say it makes sense in context but I'm not sure it does) and the reaction shot this kid gives is a priceless mixture of "Whoops!" with a resigned shrug thrown in as well. Come to think of it, every time she ends up killing someone (which tends to be quite often) is darkly hilarious. Glenn Ford is also fun as a hard-boiled cop looking into the wave of violence that seems to follow this kid around and he gets a really good death scene. It happens a little earlier than one would expect, but them's the breaks I guess.
Add to that the bombastic music score that doesn't fit the film at all, a plot that takes Rosemary's Baby, The Omen, The Exorcist and a few others and smashing them together and you get a one of a kind film they just don't make anymore. I'd give more details, but this really is the sort of film you should go into with as little info as you8 can muster. It makes the bizarre stuff a little easier to take.