Harriet Martens is a tough cop, but now two of her officers have been murdered within hours of each other - the circumstances of their deaths echoing the Book of Exodus' "a life for a life, and eye for an eye". Harriet must now muster all her strength to prevent a serial killer completing a gruesome plan of revenge.

Harriet Martens, named ‘The Hard Detective’ by the media because of her unrelenting opposition to every sort of evil-doing, has been secretly summoned to London to investigate corruption in the country��s most prestigious crime-fighting team, the elite Maximum Crimes Squad. And she suddenly finds herself under fire. Not only is she opposed at every turn by the head of the Squad, but she is menaced by other, more mysterious, figures.

Whilst relaxing with her husband at the Majestic pool one hot August bank holiday, Harriet Martens does not expect the refreshing glass of Campari soda at her side to conceal a deadly drug. When she awakes from a doze she is no longer by the water, but in a hospital bed recovering from a near fatal dose of aconitine. As Harriet makes a slow recovery, she tries to come to terms with the fact that someone wanted to kill her....

Detective Superintendent Harriet Martens resolves to resign after the new assistant chief constable at the head of the CID makes her feel inferior in her job. However, her thoughts of resignation are abruptly interrupted when the pro-hunting politician Robert Roughouse suspiciously collapses during one of his vehement speeches at an antihunting demonstration. Sensing that someone has deliberately attempted to murder Roughouse, and seeing an opportunity to prove her worth to the ACC, Detective Martens determinedly takes charge of the investigation.