Horror
As in many other Poe stories, horror is a central theme. The narrator introduces this theme in the third paragraph of the story when he describes the effect that Morella's readings have on him: "And then, hour after hour, would I linger by her side, and dwell upon the music of her voice, until at length its melody was tainted with terror, and there fell a shadow upon my soul, and I grew pale, and shuddered inwardly at those too unearthly tones. And thus, joy suddenly faded into horror. . . ."