The phrase “nature versus nurture” is used to describe the debate about the relative influence of genetic inheritance and environmental influence on human development. In The Locked Door, the question is raised as to whether Nora inherited a tendency toward violence from her father, convicted serial killer Aaron Nierling. Although Nora repeatedly insists that she is not like her father, she also seems to fear passing his genes on to her children, indicating that she does believe violence can be inherited.

Throughout the novel, Nora argues that she’s “not like [her] father” (37, 268), “not a murderer like he is” (160), and “not a monster like he is” (230). Nora uses her career as a surgeon as evidence of the difference between them, explaining that, while he murdered multiple women, “[She] save[s] lives” (37). Nora’s repeated, intentional denial of similarities between herself and her father is a reflection of her belief—and her hope—that environment can overpower genetics.

Despite these denials, Nora’s narration reveals that she worries about the genes her father passed to her. She decides not to pursue romantic relationships or build a family because they “do share the same blood” (160), and she “can’t risk passing on [her] genes to anyone else” (171).