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

Family lies and secrets is a key motif in No One Can Know, illustrating the themes of The Complex Bonds of Sisterhood, The Domestic as a Dangerous Space, and The Psychological Effects of Abuse and Trauma. The novel’s very title sows the motif of secrets into the plot. Additionally, lies and secrets are important narrative devices, building its suspense and mystery elements. For example, the author reveals Daphne’s secrets only in the Epilogue, ensuring the plot remains propulsive until the end. Daphne’s secrets may be revealed to the viewer, but are still an enigma to her sisters, adding a note of mystery and thrill even to the decisive ending of the book.

The author shows all the Palmers keeping secrets from each other and the outside world. They do this to both protect their private selves and exert control over other family members. JJ, for example, keeps her sexuality and uninhibited self from her family, putting on an obedient, demure act. Similarly, Daphne makes herself invisible so she can watch everyone and learn their secrets.