Susan is the central protagonist of the novel. Though she holds responsibility in Mr. Griffin’s murder, she is the most redeemable and relatable character in the novel. Susan becomes involved in Mr. Griffin’s murder through peer pressure. She is not present for many of the decisions that lead to Mr. Griffin’s death, but she is ultimately culpable because she not only doesn’t reveal the truth to the police, but she lies about Mr. Griffin having an affair and leaving Cathy. Susan’s home life is a major system of support, and her mother is formative in rebuilding Susan’s sense of self after Susan nearly dies. Susan’s internal conflict is one that many teenagers endure. She is awkward, perceived as nerdy, lonely, and self-conscious. These internal conflicts make her succumb to a peer pressure that ultimately leads to murder, serious consequences, and a reckoning with who she truly is.

Mark is the primary antagonist of the novel. He is a psychopathic teenager whose deeply disturbed behavior is successfully disguised by his manipulative personality. Mark has an innate ability to spot other peoples’ weaknesses. He knows how to take advantage of those weaknesses to fit his own narratives and goals.