The first-person unnamed narrator describes his struggle with "attacks of the singular disorder which physicians have agreed to term "catalepsy", a condition where he randomly falls into a death-like trance. This leads to his fear of being buried alive. He emphasises his fear by mentioning several people who have been buried alive. In the first case, the tragic accident was only discovered much later, when the victim's crypt was reopened. In others, victims revived and were able to draw attention to themselves in time to be freed from their ghastly prisons. The narrator reviews these examples in order to provide context for his nearly crippling phobia of being buried alive…
(Excerpt from Wikipedia)