An aging, physically incapacitated Hercule Poirot returns to the site of his first case to prevent a calculated series of murders before his own death. Confined to a wheelchair and struggling with failing health, Poirot enlists his long-time associate Captain Hastings to act as his eyes and ears among the guests at Styles. The narrative unfolds through Hastings' perspective, documenting his growing unease as he attempts to identify a cunning killer hiding in plain sight among the house guests. Poirot must navigate the limitations of his body while employing his sharp intellect to outmaneuver a manipulator who orchestrates deaths without ever pulling a trigger.

This novel is widely recognized as the definitive conclusion to the Hercule Poirot series, noted for its somber tone and departure from the traditional detective format. Critics and readers often highlight the poignant nature of seeing the legendary detective in his final days, stripped of his physical vitality but retaining his mental acuity. The narrative is frequently praised for its complex moral questions regarding the limits of the law and the nature of the criminal mind. It remains a significant entry in the canon, serving as a calculated and reflective end to one of the most famous characters in mystery fiction.