Final answer:
The story's mood changes to one of terror and horror as reflected by descriptive phrases indicating dread and unrest, leading to a mood best described as eerie and ominous.
Step-by-step explanation:
The mood in the story shifts to one of terror and horror when Alicia becomes ill. This mood can be depicted by the word choices in the provided text. Phrases like “his ordinary manner had vanished”, “hurried, unequal, and objectless step”, “more ghastly hue”, and “tremulous quaver, as if of extreme terror” indicate a significant change to a darker, more ominous atmosphere.
These descriptions evoke a feeling of dread and unrest, contributing to a mood that can be best described as eerie and ominous (Option B).