"Poltergeist III" is the weakest in the "Poltergeist" trilogy. It is pretty dumb with a lot of plot holes, but it does have some good effects. The ghosts make contact through mirrors in this film. It's a neat idea, but it's overwhelming. There are too many scenes with mirrors. It gets pretty ridiculous.
Kane is back, but he is not played by Julien Beck, since he died. Instead, the producers got some actor to wear make-up to resemble Beck. It doesn't work nearly as well. He is not creepy at all.
Zelda Rubinstein is back and she is good in her performance. There are some pretty great special effect scenes involving her.
Lara Flynn Boyle plays Heather O'Rourke's cousin and she does a good job. She is very good.
This is Heather O'Rourke's last film of her career. She died during post production at 12 years old. She had some sort of intestine disease and she ended up dying of a heart attack. It is very sad. People believe that there is a "Poltergeist" curse because someone dies after each film. Heather O'Rourke after the third film, Julien Beck died of cancer after the second film, and Dominique Dunne was murdered after the first film. It is a strange coincidence.
"Poltergeist III" is just an OK film, but it is a good time. It completes an above average horror trilogy.