In the public imagination, a "psychopath" is a violent serial killer or an over-the-top movie villain, as one sometimes might suspect Frank to be. He is highly impulsive and has a callous disregard for the well-being of others that can be disquieting. But he is just as likely to be a next-door neighbor, a doctor, or an actor on TV—essentially no different from anyone else who holds these roles, except that Frank lacks the nagging little voice which so profoundly influences most of our lives. Frank has no conscience. And as much as we would like to think that people like him are a rare aberration, safely locked away, the truth is that they are more common than most would ever guess.
Psychopathology is explained in frightening detail at Damn Interesting. (Incidently, the "Frank" referred to in the quote was not pictured. This picture is of psychopath and serial killer Ted Bundy.) Link