Margaret is the protagonist of The Thirteenth Tale. She works for her father at his bookshop, which specializes in old and antique texts, but is also an amateur biographer. Margaret is intellectual and solitary and loves 19th-century literature, more specifically works like Jane Eyre that fall under the category of gothic literature. Because she is the narrator of the present-tense narrative thread of the novel, the reader gets little sense of what Margaret looks like. There are various glimpses as she looks into a mirror, or glass. When she sees her own reflection, although she attributes it to her twin, the reader can understand it as a description of Margaret herself: “A white-faced waif with dark eyes, a hazy uncertain figure trembling inside the old frame” (131). The reader also receives indirect characterization of Margaret from the other characters, who all appear concerned for her health and encourage her to eat more.

Margaret’s own history plays a large part in the narrative, which weaves her own experience of being a twin with the story of Emmeline and Adeline. Margaret and her sister Moira were attached at birth and shared Margaret’s heart.