Villains & Enemies; Seen & Unseen

The essence of a successful suspense story is a great villain. Intelligent and charismatic, plus enough of a sociopath to engage in single-minded pursuit of his or her goal no matter what. In a really good story, the villain is on the page, hiding in plain sight, and yet invisible to both the reader and the protagonist. The villain should also be a chameleon, changing its MO periodically to