Constantine is a movie starring Keanu Reeves and is based on a comic book series by DC Comics; the character of John Constantine is known for hunting demons and sending them back to hell. Just as Constantine’s actions implicitly mirror Lark’s serial killings, the film is also thematically tied to Lark’s developing relationship with Lachlan. Early in the novel, for example, Sloane tells Lark that Lachlan looks like Keanu Reeves from Constantine. This is Lark’s favorite movie, and the film also becomes symbolic of Lachlan’s growing understanding of Lark’s true identity. When Lachlan is initially struggling to understand Lark, he finds her various trophies from her kills hidden behind her poster of Constantine, and this implies that Lark feels a kinship with the character when she engages in killing other serial killers.

Later, while trying to fall asleep at the insomnia retreat, Lark asks Lachlan to read to her, and he reads her the script of Constantine. Because of this, Lark asks him how many times he has seen it, and he admits, “Twelve, I reckon” (233). This also reveals Lachlan’s character, for he had never seen the movie before meeting Lark. While it might seem simple to watch a love interest’s favorite movie one time to better understand her, Lachlan watches the film repeatedly and memorizes every detail.