Psychos

I find myslef increasingly wanting to take on the challenge of writing a novel from the perspective of the pshyco.  How the progression goes from normal or semi normal to full blown pshycotic with murderous desires fascinates me. What is it that triggers the onset of madness? Guess I'll do some research and begin putting together a story.  I might decide to make it two insane people working in tandom, maybe a brother sister combo and have them be super twisted.  The possibilities are endless I suppose. I just have to pick one and go with it.