When Hercule Poirot discovers a bullet hole in a young woman's hat, he realizes that a series of near-fatal accidents are actually calculated attempts on her life. While vacationing in Cornwall, the famed Belgian detective and his companion Captain Hastings find themselves drawn into a web of deception surrounding Nick Buckley, a woman whose life is under siege by an unknown assailant. Poirot must navigate a complex social circle and decipher conflicting testimonies to prevent a murder before it occurs. The narrative unfolds through the observant, methodical lens of Poirot, who relies on his psychological acumen to expose the truth hidden beneath polite facades.

This novel is widely regarded as a quintessential example of the Golden Age of detective fiction, praised for its intricate plotting and clever misdirection. Critics and readers alike have noted the ingenuity of the central premise, which subverts the traditional murder mystery by focusing on the prevention of a crime. The characterization of Poirot remains a highlight, showcasing his ability to find order in chaos through his sharp intellect. The work continues to be studied for its structural precision and its enduring influence on the mystery genre as a whole.