Kate Alice Marshall’s No One Can Know (2023) is a tense psychological thriller and murder mystery. Marshall’s second novel for adults, No One Can Know follows Emma Palmer, whose parents were mysteriously shot dead 14 years ago. As a financial crisis forces Emma and her husband, Nathan, to return to her ominous childhood home, Emma reconnects with her estranged sisters, Daphne and JJ, and begins to discover uncomfortable family secrets. Tackling themes like trauma and sisterhood, Marshall infuses psychological realism in her fast-paced and twisty narrative. The novel is a USA Today bestseller.

Marshall is the prolific author of young adult (YA) and middle grade (MG) novels such as I Am Still Alive (2018) and Extra Normal (2023). She published What Lies in the Woods, her first book for adults, in 2023. Marshall often uses suspense in her plots and combines genre conventions with insights into her characters’ psyches.

This guide refers to the Flatiron Books 2023 e-book edition.

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

Plot Summary

When 30-year-old website designer Emma Palmer discovers she is pregnant and her husband, Nathan, loses his job, the pair move back to her childhood home. Locked-up for decades, the Palmer house has a bleak history. When Emma was 16, her wealthy but abusive parents, Irene and Randolph Palmer, were shot dead in the house. The police never recovered the murder weapon. Emma, who was rebellious and openly feuded with her parents, was blamed for the murders along with her friend Gabe, who was falsely rumored to be her boyfriend.

The night of the murders, Emma visited Gabe to vent about their abusive treatment. When she returned home, she found her parents dead and Daphne and Juliette at home. Daphne’s clothes were mysteriously soaked in blood, and Juliette wore unfamiliar clothes. Assuming one or both was involved in the deaths, Emma destroyed the clothes, letting the police blame her. Short on proof, the investigation fizzled out. Juliette left home, and Emma and Daphne went to foster homes. Since then, Juliette and Daphne have avoided Emma.

Emma texts her sisters that she has moved back into their parents’ mansion. Juliette, who now goes by JJ, re-enters Emma’s life, worried that Emma may uncover secrets JJ wants left buried. As a teenager, JJ, who ostensibly obeyed her parents, had a secret life, sneaking out of the house to party at night. JJ was out the night of her parents’ murder and has little memory of it. However, JJ believes she may have killed her parents because she does remember standing near her parents’ bodies with a gun. Daphne, who lives close by, secretly keeps close watch over Emma, even installing a location tracking app on her phone. Growing up, Daphne was the quietest of the three sisters and had an avid interest in poisons and botany. She and Emma were especially close.

Meanwhile, frustrated by the persistent rumors that she murdered her parents, Emma decides to investigate. She discovers that her father, Randolph, headed a cartel that robbed trucks and cargo, while her mother, Irene, was having an affair with Rick Hadley, the police officer who was Randolph’s best friend. Irene, who discovered Randolph’s criminal activities and wanted to leave him, stored evidence against him in a flash drive. Daphne saw the contents of the flash drive the night their parents died.

As Emma learns her family secrets, her marriage frays. Nathan is having an affair and wants to sell the Palmer House to get the money in a joint account before divorcing Emma. Matters come to a head when Emma finds Nathan shot to death in the outhouse of the property. Though the murder weapon is missing, forensics reveal the same gun was used to shoot Irene and Randolph. Nathan called the police hours before he died, suggesting that he found the lost flash drive, which was not found at the site of his murder. Emma becomes the prime suspect in Nathan’s murder, and the police may reopen her parents’ murder investigation, as well. JJ, beginning to soften toward Emma, takes her to meet the family lawyer. On the way back, Hadley stops their car.

Hadley attacks Emma, demanding the flash drive. Daphne, who has been tracking Emma’s phone, arrives and smashes a rock against Hadley’s skull, nearly killing him. JJ spontaneously recalls that she did not kill her parents, but came home to see Irene shoot herself in the chest. Shocked, JJ briefly picked up the gun. In the present, Emma and JJ report Hadley’s attack, and the police find the flash drive and the gun used to kill the Palmers and Nathan at Hadley’s house. The drive contains evidence linking Hadley with Randolph’s criminal cartel. The police believe Hadley killed the Palmers because of a business deal gone wrong. He killed Nathan because he found the flash drive while cleaning the house. It is also revealed that Hadley sent anonymous threatening letters to the sisters for many years, leading JJ and Daphne to stay away from Emma. Emma is exonerated and the sisters reunite, but Emma knows the police’s theory does not reveal the full truth.

As the novel ends, JJ and Daphne dote on Emma’s baby girl, Wren. Emma and Gabriel are finally a couple. Daphne reveals in an internal monologue that she, not Hadley, killed Nathan and Randolph, who caught her going through the flash drive and made a phone call about settling the matter. Fearing Randolph meant to harm her and her sisters, Daphne shot him. Irene heard her shoot Randolph and took the gun, telling Daphne to leave to save herself. Irene shot herself at the exact moment JJ came in. JJ briefly picked up the gun and, in a state of shock, left the house for some time while Daphne hid the flash drive and the gun in the outhouse. When Emma returned home, she made her sisters change clothes before calling the police. Daphne killed Nathan because she discovered his affair and because he found the gun and flash drive. After murdering Nathan, Daphne planted the gun and the drive in Hadley’s house. Thus, Daphne emerges as the mastermind of the plot.