Sorry, I don't have much time to write. I am not a psychologist but have known one for 25 years. She said that Scott Wilson portrayed a sociopath (no conscience) extraordinarily well. I agree! She also said that Robert Blake portrayed a person with anger and impulse control who had a conscience but couldn't control himself superbly. I agree! What a chilling and tremendous film. I have seen over 2000 films and would rank this in the top 100. My lifelong friend deals with clients such as these regularly. My only criticism was the preachy narration at the end of the film. Many people grow up in less than ideal circumstances but only one in a million will behave as these 2 losers did.