Sapphira was a fashionable young woman in Winchester when she married Henry Colbert, a man beneath her station, and moved to a rugged backwoods village, where they have lived for more than 30 years. Twenty of Sapphira's slaves came with them. This caused somewhat of a sensation among the poor, non-slave owning population of the region, where even to this day the Colberts are admired but not well-liked. Henry successfully took over the village grinding mill, while Sapphira assumed the role of local granddame. They had three daughters, all of whom married and moved away. However, Rachel's husband died, and she returned to Back Creek with her two young children.

Sapphira and Rachel are lay nurses who often visit and comfort the sick. Sapphira appears to do this work out of a sense of noblesse oblige, but Rachel feels empathy for the sick and less fortunate. She sets herself above nobody. Rachel is also an abolitionist at heart (as, to some extent, is her father), but Sapphira is firmly convinced that slavery is not only necessary, but also moral. Henry, a rather ineffectual male presence in this story, has responded to Sapphira's haughty regime by gradually withdrawing. In fact, he has largely abandoned the Big House to live at the mill, which he justifies by claiming the lack of a reliable foreman.

Sapphira suffers from severe dropsy. Her swelling is so bad she can no longer walk. She is jealous of a young slave named Nancy, with whom she believes Henry is having an affair. Much of the novel describes Sapphira's attempts to get rid of Nancy, first by selling the girl in Winchester, and later (when Henry refuses to sell) by importing her ne'r-do-well nephew to rape and destroy Nancy. This doesn't work either, primarily because Rachel takes Nancy under her wing and arranges her escape to Canada via the Underground Railroad.