It was the beating of the old man's heart. It's not madness, says the narrator, "but over-acuteness" of his sense of hearing caused by his nervousness, as he says in the opening paragraph of the story. ... The narrator's obsession shifts from the old man's "Evil Eye" to the old man's loudly beating heart.
So here is the answer of the given question above. Hope this information will help you with what you are looking for. Anyway, both plot and theme are considered essential literary elements, but these two elements are different. The plot is the flow or the sequence of events within the story. On the other hand, the theme is the central or overall message that the whole story wants to convey. Hope this answer helps.
Protects you? Provides sanctuary
