A plot must involve...
* a problem
* complications
* a climax
* a resolution
Answer: quoting.
The best method for incorporating evidence in this case would be quoting. This is because the original text is easily accessible, and because, if the reader were to question your argument, he would be able to easily compare your analysis with the text. Moreover, your claim refers to the use of language in the book, which does not require secondary sources in order to be interpreted.
Answer:
The central theme in "The Masque of the Red Death" is the inevitable, or perhaps more accurately, the inescapable nature, of death. Prospero and his companions attempt to shut themselves off from the rest of the world in an attempt to avoid the horrible plague (the "red death") that is ravaging the countryside.
