Secrets are the most prominent motif in the novel. Within the narrative, secrets are both necessary and dangerous; they serve a simultaneously divisive and connective role. The Secret brings Cass and Max-Ernest together, but moreover, it predicates the reader’s connection to the story and the narrator. In this sense, secrets provide a framework for the secondary world and guide the narrator’s interactions with the reader.

Secrets are significant in the secondary Secret world. For one thing, it’s a secret world, a secondary world hidden within the ordinary one. Furthermore, its entire existence is predicated on the Secret. The Midnight Sun was formed to attain the Secret, while Pietro and the Terces Society work to protect it. Without the Secret, this secondary world would have no reason to exist. On a meta level, the book would not exist without the Secret either; the narrative is framed as a secret account about the Secret. The narrator is an arbiter of knowledge, withholding certain details for the reader’s protection but revealing others to ensure they’re prepared. Secrets, then, are a device through which the reader is implicated as a character in the narrative.

Secrets also manifest as riddles and codes.