Behind a Mask by Louisa May Alcott

For several weeks the most monotonous tranquillity seemed to reign at Coventry House, and yet, unseen, unsuspected, a storm was gathering. The arrival of Miss Muir seemed to produce a change in everyone, though no one could have explained how or why. Nothing could be more unobtrusive and retiring than her manners. She was devoted to Bella, who soon adored her, and was only happy when in her society. She ministered in many ways to Mrs. Coventry's comfort, and that lady declared there never was such a nurse. She amused, interested and won Edward with her wit and womanly sympathy. She made Lucia respect and envy her for her accomplishments, and piqued indolent Gerald by her persistent avoidance of him, while Sir John was charmed with her respectful deference and the graceful little attentions she paid him in a frank and artless way, very winning to the lonely old man. The very servants liked her; and instead of being, what most governesses are, a forlorn creature hovering between superiors and inferiors, Jean Muir was the life of the house, and the friend of all but two.

Lucia disliked her, and Coventry distrusted her; neither could exactly say why, and neither owned the feeling, even to themselves. Both watched her covertly yet found no shortcoming anywhere. Meek, modest, faithful, and invariably sweet-tempered -- they could complain of nothing and wondered at their own doubts, though they could not banish them.