Found this quote on the blog EsoterX, and it struck me as a central truth. The tracing of evil in otherwise good people is a delicious line that runs through the heart of mystery and crime fiction. It’s easy to paint a villain as totally despicable, but much more difficult — and more true to life — to deal with someone who is a 49-51 mix of good and depravity.
“If only it were all so simple! If only there were evil people somewhere insidiously committing evil deeds, and it were necessary only to separate them from the rest of us and destroy them. But the line dividing good and evil cuts through the heart of every human being. And who is willing to destroy a piece of his own heart?”