Mental Illness
This is something of an umbrella theme in the novel as there are so many sub-themes within the larger one. Each of the main characters suffers from a mental illness. Camille, the protagonist, self-harms, and her body is a maze of scars where she has carved out words into her skin that she has hallucinated before cutting. When she is suffering extreme stress she returns to cutting as a way of releasing her anxiety. The cutting stems from her childhood when her sister Marian passed away, and also results from feeling rejected by her mother who makes no bones about preferring her sister.
Although Camille's mental health issues are directed at herself, both her mother and sister's mental illness is directed at others, and in both cases results in the death of others as well. Adora suffers from Munchausen's Disease by Proxy; this is a disease that involves making others sick and getting attention through them. This resulted in her poisoning Marian and ultimately killing her.
Amma is a sociopath without feeling, empathy or conscience, although she does feel jealousy and it is this that prompts her to murder two little girls to whom her mother pays attention. Her sociopathy enables her to be highly manipulative and to almost get away with murder.
Taking the Line of Least Resistance
One of the lesser themes in the novel is the consequence of taking the line of least resistance and the person that Amma is can be partially attributed to this. Her father is a passive man who barely registers in the narrative of the novel because he barely registers in the narrative of his family either. He lets Amma do whatever she wants and is completely fooled by her fake persona because he wants to be; his line of least resistance enables his wife and daughter to kill others because he is not involved enough or motivated enough to do anything about it.
Murder
One of the themes of the novel is murder, and there are several different murders within the book. Both little girls in Wind Gap are reported missing before they are murdered; believed to have been killed by Adora they are actually murdered by thirteen year old Amma. Adora, though, is not above killing people and is responsible for the death of her daughter, Marian. Murder is also a catalyst in Camille's life for putting the past behind her. Her questions over Marian's death, and her relationship with her mother, are finally resolved, and she is able to move forward with her life because the murders of the past are finally solved.
Judging on Appearances
This theme is evidenced in many of the characters and situations within the narrative. Richard Willis is the chief offender when it comes to judging by appearances both in his personal life and his professional life too. Personally, he is horrified by the appearance of the scars on Camille's skin, but he is unable to see past them and gives up on a good relationship because he judges her character by what she has done to her body. Professionally he is also guilty of being fooled by appearances in that he is unable to envisage a sweet, popular teen girl being a murderer. Adora has the appearance of having murdered her own daughter and so Willis assumes she has murdered Ann and Natalie as well. This ultimately enables Amma to murder again.
