The general plot was that innocent couple Carol and Paul go to England after Carol's brother dies under strange circumstances. Eventually both are 'seduced' into the cult. This is an old story. Here is the interesting rub. The actress who played Carol had this LOOK that made her more 'satanic' than the others. The wanna-be satanists had lots of casual sex, engaged in disturbing behavior, and basically acted like kids on their first trip away from home. Carol, the supposed innocent of the group (and she was) had a true(r) look of power - one that said "yeah, seen that, done that, wait until the real adults arrive". Like I said, she struck me as the 'Most Likely to Succeed (in Satanism)" of the bunch.
I thought about how people play at power games, but the real agents pull off what the wanna-bes aspire to and do so without all the window dressing. The neophytes wouldn't REALLY want to meet the pros, no matter how much the neophytes believe themselves to be inheritors to the crown.