When the wealthy Emily Inglethorp is found dead from strychnine poisoning in a locked room, Hercule Poirot is called upon to solve his first major English case. The protagonist, a retired Belgian police officer living as a refugee in England, must navigate a household of suspects, each harboring secrets and potential motives for the inheritance. Opposing him is a web of deception, forged documents, and carefully planted clues designed to frame the innocent. The narrative unfolds through the perspective of Captain Arthur Hastings, providing a grounded, observational framework that emphasizes the intellectual rigor of Poirot's investigative process.

As the debut novel of one of the most prolific mystery writers in history, this work is widely recognized for establishing the tropes of the Golden Age detective genre. Readers and critics consistently highlight the introduction of Hercule Poirot as a defining moment in crime fiction, noting the precision of the puzzle-box structure. The narrative is frequently praised for its intricate plotting and the clever use of the unreliable narrator to obscure the truth. It remains a foundational text for those interested in the evolution of the whodunit format and the mechanics of classic mystery writing.