The locked door of the novel’s title also serves as the narrative’s central symbol. The locked door refers to the entrance to the basement in Nora’s childhood home, which led to her father’s supposed woodworking area. In reality, as 11-year-old Nora discovers, the locked door leads to where her father keeps his kidnapped victims and murders them, covering up the scent of his crimes through constant cleaning with lavender. The locked door thus symbolizes the secrecy and cruelty that lurks beneath Aaron’s outwardly charming public persona.

Later in the novel, Nora discovers another locked door, this time in Brady’s apartment. Nora fears the worst, wondering if she is about to discover another terrible secret. Instead, the door opens onto a child’s bedroom, which belongs to Brady’s young daughter, Ruby. The symbolism of this second door thus suggests that a happier life awaits Nora, invoking loving connections and domestic peace instead of the terror and violence of her childhood home.

The stray cat hanging around Nora’s house, which she eventually adopts, acts as a symbol of Nora’s humanity throughout the novel. As a child, Nora kills the hamsters and mice her parents give her as pets. As an adult, she feels that it’s “not safe” for her to have a cat as a pet, suggesting that she feels she lacks the basic humanity to care for another living being.