The quote suggests that understanding the nature of a killer requires deep introspection. It implies that the reasons behind someone's capacity for violence are not always external but can be found within oneself. The imagery of a hypodermic needle, wood, stones, and mirrors symbolizes the search for truth and self-reflection. It hints that discovering the darker aspects of humanity is essential to grasp the motivations for such extreme actions.

This perspective encourages readers to confront their own potential for darkness rather than dismissing it outright. The line emphasizes that everyone has the capacity for harm under certain circumstances, prompting a dialogue on morality and human nature. By asking readers to look internally, it challenges societal perceptions of killers as entirely 'other,' urging a more nuanced understanding of the human psyche.