When a mysterious, mud-caked visitor collapses at his doorstep, Hercule Poirot is thrust into a high-stakes confrontation with a global cabal determined to achieve world domination through systematic murder. Poirot must navigate a series of lethal traps and near-death encounters orchestrated by the elusive 'Big Four'—a quartet of international criminals representing the pinnacle of criminal intellect, wealth, science, and violence. As the detective and his loyal companion Hastings attempt to dismantle this organization, the narrative shifts between investigative deduction and survival, culminating in a dramatic explosion that threatens to end Poirot's career permanently. The story unfolds through a series of episodic encounters, testing the limits of Poirot's analytical prowess against an enemy that operates beyond the reach of conventional law.

This novel represents a departure from the traditional locked-room mysteries typically associated with the author, leaning instead into the conventions of the international thriller genre. The premise suggests a focus on grand-scale stakes and a more action-oriented narrative than the standard Poirot investigation. Readers often note the unusual tone of the work, which prioritizes the threat of a global conspiracy over the intricate puzzle-solving of earlier entries. The narrative structure reflects the author's experimentation with pulp-style adventure, creating a distinct entry within the broader detective series that challenges the protagonist in a more physical capacity.