From The Fall of the House of Usher

And now, some days of bitter grief having elapsed, an observable change came over the features of the mental disorder of my friend. His ordinary manner had vanished. His ordinary occupations were neglected or forgotten. He roamed from chamber to chamber with hurried, unequal, and objectless step. The pallor of his countenance had assumed, if possible, a more ghastly hue --but the luminousness of his eye had utterly gone out. The once occasional huskiness of his tone was heard no more; and a tremulous quaver, as if of extreme terror, habitually characterized his utterance. There were times, indeed, when I thought his unceasingly agitated mind was labouring with some oppressive secret, to divulge which he struggled for the necessary courage. At times, again, I was obliged to resolve all into the mere inexplicable vagaries of madness, for I beheld him gazing upon vacancy for long hours, in an attitude of the profoundest attention, as if listening to some imaginary sound. It was no wonder that his condition terrified-that it infected me. I felt creeping upon me, by slow yet certain degrees, the wild influences of his own fantastic yet impressive superstitions.

Edgar Allan Poe