O’Brien uses the framework of a traditional thriller or mystery novel; however, contrary to the conventions of the genre, he denies the reader a final answer or a tidy solution to the mystery.

O’Brien uses some of the literary conventions of the mystery genre—such as the disappearance or murder of an important character—but then subverts the genre’s tenets for his own purposes. In mystery novels, the perpetrator of a crime is usually caught and punished for their misdeeds, restoring balance and making the world right again. O’Brien exposes the naïve belief that, by punishing wrong-doers, the world can be made whole again. In doing so, O’Brien uses the mystery genre to reveal the complete lack of certainty in life and the frailty of human belief in an ultimate truth. He denies his readers the comfort of a morally tidy ending. He also undermines the value of certainty by indicating, through the trickster John Wade, that an illusion can easily appear to be truth.

At the center of this disturbing novel, O’Brien’s most significant theme remains the unknowable mystery of the human heart and the nature of love. For O’Brien, the working of the human heart is ultimately unknowable; the most profound mystery.