Anna Witherall's carefully constructed life of success and happiness is threatened by a dark secret that forces her into the world of secret intelligence. Married to her university boyfriend David, with whom she has three-year-old twin daughters, Stella and Rose, Anna works for an aspirational magazine. However, her hidden past and a dangerous entanglement with espionage compel her to question her family's safety, leading to the agonizing decision to leave her children forever. The narrative is framed by the constant threat of being watched by someone she trusted, who is intent on retribution.

Stylish and assured, 'The Most Difficult Thing' is described as an irresistible combination of contemporary espionage and domestic suspense. The narrative is characterized as a compulsive and highly charged examination of betrayal, focusing on the difficult choices a protagonist must make to protect her family. The premise sets up a tense exploration of secrets, trust, and the lengths one will go to for the truth. The blend of espionage thrills with intimate domestic stakes suggests a fast-paced and emotionally resonant reading experience.