Haunted by a fractured memory of a childhood trauma, Aurora del Valle embarks on a quest to uncover the hidden truths of her past. Raised in the opulent, restrictive society of late nineteenth-century Chile by her formidable grandmother, Aurora enjoys a life of relative independence while struggling with persistent, inexplicable nightmares. Following the collapse of a significant romantic relationship, she turns her focus toward the secrets buried within her family history. The narrative, presented with Allende's characteristic focus on lineage and memory, follows Aurora as she navigates the social hierarchies of her era to confront the events that defined her early life.

Portrait in Sepia is widely regarded as a significant expansion of the author's established literary universe, effectively bridging the narratives of her earlier, more prominent works. Critics often highlight the novel's meticulous attention to historical detail and its ability to weave personal identity into the broader fabric of Chilean history. Readers frequently note the atmospheric quality of the prose, which captures the shifting social tides of the late nineteenth century with precision. The novel is generally viewed as a sophisticated examination of how inherited trauma and hidden family histories shape the trajectory of individual lives. Its reception reflects a consistent appreciation for the author's ability to maintain thematic continuity across a sprawling, multi-generational saga.