In "Insidious Intent" by Val McDermid, the story revolves around a relentless man driven by his obsession. His fixation propels him into a dark journey as he seeks to fulfill his dangerous desires, leading to a series of troubling events. The plot intricately explores the psyche of individuals consumed by their obsessions and the lengths they will go to achieve their goals.

The narrative weaves suspense and drama, showcasing the complexities of human behavior. As the protagonist navigates through his inner turmoil, readers are drawn into a chilling exploration of what it means to be captivated by an idea, and the potential consequences when that idea turns sinister.