Lady Dorothea de Plessis FitzClarence, known as Erin, is the protagonist and one of the first-person narrators of One by One. Erin is one of two live-in staff members at Chalet Perce-Neige; she takes care of most customer-facing concerns while her work partner, Danny, is the chef. Erin and Danny enjoy each other’s company but do not share details about their pasts, which Erin is content with at the beginning of the novel.

Erin’s appearance is not emphasized heavily in the novel, but Liz describes her as “pretty and tanned, with shiny chestnut hair […] She looks self-possessed, assured” (35). One important detail that is referenced several times is the scar on her cheek, “the thin, pink tracing of a long scar that runs across her right cheekbone, disappearing into her hair” (35). It is noted that it could be hidden with makeup but Erin has not done so. The scar represents her grief and guilt over the deaths of her brother and boyfriend, making it an active symbol of Erin’s history.

The reader does not learn much about Erin’s past, as much of her life has been defined by the avalanche event when she was 19. Although she is technically nobility, she had a relatively simple upbringing and never felt comfortable around the wealthy.