"K" is a mystery novel written by Mary Roberts Rinehart. The story revolves around the character K, an enigmatic and wealthy man who is found dead under suspicious circumstances. The plot unfolds through the perspective of an unnamed narrator, a nurse who becomes entangled in the investigation of K's death.As the story progresses, the narrator delves into the complex web of relationships within K's wealthy and secretive family. The family members all have their motives and secrets, making the investigation even more intricate. The novel combines elements of suspense, intrigue, and psychological tension as the narrator uncovers hidden truths about K and his family.