Floating between July 2007 and September 2017, Marshall's thriller is narrated by two characters, Olivia and Ellen. Olivia sits in a London courtroom waiting for the imminent arrival of her son, Daniel. Ellen wonders what has happened to her flatmate, Sasha. As the days pass and there's still no there's no sign of her, a nagging whisper in Ellen's head grows louder. What if Adam is back? What if he's had enough of his new life in Scotland? What if he has been waiting, biding his time, lulling us into a false sense of security?

Ellen's worried voice seeps around the locks she's constructed to keep it out. Daniel Monkton was sentenced to ten years in prison, but now he's out, free to go where he pleases and contact whom he likes. Ellen is certain Daniel is back and that he wants to make Ellen, Sasha and best friend Karina pay for what they did.

For the first hundred pages or so, Three Little Lies is all atmosphere and illusion as the strands of the past unravel as Ellen always knew they would. It all begins when Karina hounds Ellen, the day the Monktons moved into the house on the corner. Ellen is used to the comfortable familiarity of her friendship with Karina but unable to resist the pull of the Monkons--the house with books, music and Sasha's exotic parents, as well as dark-haired brothers Daniel and Nicholas.

Back in 2017, Ellen can't stop the deepening leaden feeling and panic she's been trying to suppress. She never discussed Daniel's trial, not properly. When there's a knock at the door, she prays that its Sasha's boyfriend, Jackson, and that he's going to tell her Sasha has turned up at his flat, contrite and armed with a reasonable explanation. While PC Bryant tells Ellen that the vast majority of missing persons turn up safe and well within a day or two, Ellen bemoans Jackson's possessiveness as he drones on and on about how he isn't the man for Sasha and how she was always trying to paint herself as some sort of tragic heroine in her own life story.

Ellen follows one lead after the next, joining the dots until a new lead is found. She is convinced that Daniel Monkton is one step behind her, out to seek revenge for his "wrongful imprisonment." She finally confesses to Detective Bryant that

"when we were younger, the Monktons' older son, Daniel, he raped one of our friends at a party. Sasha and I testified against him at the trial. He was...angry with us. He blamed us, partly at least."

Left alone in her flat, Ellen's paranoia becomes "a phantom twisting and hiding, forever slipping out of her grasp." Marshall also illustrates Olivia's moral dilemma as "the rapist's mother" as she tries to battle the false accusations that have ruined her and Daniel:

I was so stupid, so self-satisfied, so complacent. I'd painted myself as the benevolent matriarch of this alternative, relaxed, welcoming household, when in fact I was sitting on a nest of vipers.

The story is refracted through the prism of Karina's court confession. Was Karina a naïve, helpless victim, a mere girl taken advantage of in the most horrible way by a sexual predator? Was Sasha just a troubled young woman who for reasons unknown developed a vendetta against Daniel? Sasha's past is revealed in layers, and the reader isn't quite sure how all of this is going to come together. If Daniel is lying, Ellen realizes that she's siding with a world that thinks it's a woman's own fault if she gets raped, a world that doesn't a woman even when she has the scars to prove she's been hurt.

Maybe Ellen's security had been an illusion, a ten-year masquerade only now approaching its final act. She recalls the classical music she learned to love from being in Olivia Monkton's orbit, and her remorse when she was rejected by their world. Three Little Lies is not a heart-pounding thriller but a dark and plodding one, a puzzling out of events that will forever change Ellen and Sasha's lives as the past and the present circle back to Daniel, be he master manipulator or the victim of everyone's lies.