Once the sociopath has the victim “hooked” and under their control, that charming person you first met, seemingly disappears. And the mask comes off and the true person that they really are comes out. And it is the opposite of the person you ‘thought’ you knew. And in most cases, it is too late. They have figured out ANY weaknesses, insecurities, and vulnerabilities that you have. They take these "weaknesses" and use subtle ways to make you feel that this weakness is so ugly, that if anyone was to find out you have this trait, you will be ostracized from society. You probably have also confided in them, since they presented themselves as understand, sympathetic, and kind.
You soon learn that this person is anything but Kind, Understanding, and Sympathetic.