When a prominent physicist is found dead after summoning help to protect a national security secret, Hercule Poirot must identify the killer among a house full of suspects. Poirot arrives at the Surrey estate of Sir Claud Amory only to find the scientist deceased and a critical formula missing from his safe. Accompanied by his loyal associate Captain Hastings, the detective navigates a web of familial tensions and hidden motives to uncover the truth. The narrative follows the traditional structure of a closed-room mystery, emphasizing logical deduction and the interrogation of a confined group of potential culprits.

This novel is widely regarded as a faithful and engaging adaptation that successfully translates the theatrical tension of Christie's original play into a readable prose format. Readers often appreciate the opportunity to see Hercule Poirot in a classic, contained mystery setting that mirrors the structure of his most famous cases. The collaboration between Charles Osborne and the Christie estate is frequently noted for preserving the authentic voice and pacing of the author. While some purists prefer the original stage version, the consensus suggests that this adaptation serves as a satisfying addition to the broader Poirot canon for those who enjoy traditional detective fiction.