How does an author create the unsettling atmosphere of psychological suspense?

There are four major steps that an author most follow when he wants to create an unsettling atmosphere of psychological suspense. The fiction genre is generally used for this purpose.

First, the plot has to be developed using mental activity instead of physical activity. Second, whether admitted or discovered there most be madness, and it has to be accentuated, prioritized or emphasized in order to be effective. Third, a different an ambiguous protagonist must be included by the author. Fourth, direction, control and specific attention to detail on the writing style is imperative. Only by following these steps, is the author ready to control and present the reader with an unsettling atmosphere of psychological suspense.

The Pit and the Pendulum by Edgar Allan Poe who is a master in creating a sense of unsettling atmosphere of psychological suspense, is an excellent example with these characteristics. Through the use of uncommon dashes, and carefully selected words to help the reader visualized the actual motion of a pendulum that is systematically getting closer, Poe is able to create a horrific image that is very unsettling and specifically directed at the reader´s senses.