Content Warning: The novel contains descriptions of emotional and domestic abuse, anti-LGBTQ+ bias, and references to suicide.

No One Can Know is best described as a murder mystery and psychological thriller, though it also includes many tropes common in Gothic fiction. The novel uses setting, atmosphere, and psychological horror to deepen its plot and themes. One of the staples of Gothic fiction is an ominous building, often used as a metaphor for its occupants’ troubled psyches. The Palmer House and its grounds follow this convention; though lavish from the outside, the house harbor terrible secrets, such as extreme abuse and criminal activity. The house’s history as the site of Randolph, Irene, and Nathan’s murders also gives it a foreboding mood. Marshall modifies the Gothic-fiction trope of the ominous house to emphasize the novel’s domestic horror and psychological realism. For example, instead of the creepy statues and dark corners of Gothic houses, the author heightens ordinary elements of the house, such as the piano or wallpaper, into symbols of danger. This shows that everyday, seemingly ordinary domestic spaces can be sites of extreme fear and oppression.