Content Warning: This section of the guide includes discussion of illness, child death, child sexual abuse, emotional abuse, suicidal ideation, and substance use.

Mackenzie’s unnamed hereditary condition acts as a symbol of the secrecy surrounding her family. This secrecy begins with the fact that Mackenzie’s narration never names the condition, describing it only as “some inherited condition that [she] need[s] to take pills for” (7). Mackenzie does not share her diagnosis with the people she believes are her parents. Although Mackenzie cried after she got the diagnosis and tried to talk to her mother, the woman posing as Elizabeth ignored her, so Mackenzie chose not “to tell her out of spite, imagining how one day, [she] would just drop dead, and she and Dad would regret that they never paid more attention” (59). As she begins to distrust her parents, Mackenzie begins to wonder if, “considering that it’s a genetic condition, maybe Mom even knew about it all along and […] knew it could get out of hand untreated” and that “maybe that was the reason she got a life insurance policy for [Mackenzie]” (59).

In these early chapters, Mackenzie’s unnamed hereditary condition is shrouded in secrecy: First, she hides it from her mother, and then she wonders if her mother intentionally hid it from her. At the end of the novel, the hereditary condition is the key to uncovering the secret of her true parentage. While at the home of Professor John Robertson, Mackenzie discovers a prescription used to treat “[her] hereditary condition, passed on usually from a parent” (324). The realization that Mackenzie and John both have the same condition leads her to realize that John is her biological parent.