Just about everybody but Lee was a FOOL in this film. (Spoilers!)
Well not everybody but lets look at some of the less-than-intelligent actions in this film.
Sasha: She sees the Gorgon and quickly looks away in time as you can see she didn't turn to stone. Only to TURN AROUND for a second look!! Brilliant!
Dr. Namaroff: At the climax he sees Megara at the top of the stairs so he picks up the sword and covers his eyes and heads up the stairs to run her thru. But then decides to take a look!!
The Inspector: If he really wanted to get to the bottom of it all he would have co-operated with Prof. Meister instead of butting heads with him.
Paul: When Carla asked him to take her away from Vandorf and thusly away from Magara's spirit using her as a 'host', Paul refuses. But after Meister insinuates that she might be the 'host' he refuses to accept it out of blind love but nevertheless he sends her away (too late).
Mind you what good would it do to take Carla away when she'd turn into the Gorgon anyways no matter where she went? Unless Megara's spirit actually resided in the castle and summoned someone to her to be her temporary vessel and Carla was the unlucky one who got too close to the castle one night and got 'hooked'.
Lastly Paul saw the Gorgon's reflection in pond earlier on and ran from it only to come face-to-face with her. But he only got grey hair for the ordeal. Obviously because he only saw her in shadows he didn't get the full affect.
But then in the climax he sees her in the mirror, knows what she's capable of and instead of making a run for it...TURNS AROUND and looks RIGHT AT HER!
Mind you, it looks like she was using some kind of telepathic mind control to make him do it. Perhaps just like what she used on his father Prof. Heitz.