Forgotten gem from the 80s

I only remembered this film due to the sad passing of Brian Dennehy. He played a father trying to rescue his son from a religious cult. Peter Fonda was very creepy as the cult leader. I remember James Woods as the man hired to de-programme cult members.

This never gets shown on television,but it's a great story about a family traumatised by the loss of their son into a world they do not understand. Catch it if you can.