Old Mortality by Katherine Anne Porter is a short novel set in the South at the turn of the twentieth century. The narrative revolves around the impressions that two sisters, Maria and Miranda, gain from the family members around them.

Maria and Miranda's Aunt Amy, who is described as a great beauty who died tragically young, is a frequent topic of discussion. Harry, the girls' father, displays the same sense of a strong longing for the past as the other members of the family. As these stories of the past are relayed, the young girls form strong impressions in their minds about the figure of Aunt Amy, who served as an apotheosis of femininity. The girls are subsequently compelled to emulate her.

However, it is later revealed that the family's frequent reminisces about the beautiful, deified women of their ancestry conveniently discounts Great-Aunt Keziah and the girls' cousin Eva, who is homely in appearance, described as having a "chinless" face. Eva presents a sharp, prosaic contrast to the poetic, ephemeral, and dramatically sorrowful specter of Aunt Amy that has been conveyed through the family's stories. Cousin Eva, far from conforming to the archetype of Southern womanhood, fought staunchly for women's suffrage.

Moreover, the girls' exposure to stories of family relationships shows them the hatred that simmers in the human heart when they meet Miss Honey, Uncle Gabriel's second wife. Uncle Gabriel was first married to Aunt Amy, and her name stands in sharp contrast to the blatant bitterness that she exudes toward her husband's family, no doubt a result of constantly being eclipsed by the overbearing memory of Aunt Amy (preserved through the chronic and persistent nostalgia of the family).

The first time Miranda runs into Cousin Eva is when she travels by train to attend Uncle Gabriel's funeral. Both cousins display a rebellious streak and chart their own course: Miranda has married against the wishes of her father, and Cousin Eva has managed to break free from the constraining presence of the shallow beauty of her mother and sister—both now dead. Eva opens up to Miranda, and the cruelty and hostility that are hidden under the veneer of Southern gentility is revealed. Cousin Eva, in comparison to the peerless Aunt Amy, describes how she was always made to feel deficient and worthless.

Miranda's experience with Cousin Eva on the train—and the subsequent reception the two of them receive from Harry—strengthens Miranda's resolve to carve her own destiny and not be sucked into the romanticized notions of the past constructed by her father and the rest of her family. Likewise, Miranda develops a conviction to reject the bitterness Cousin Eva fosters.