The Big Four is a 1927 detective novel by Agatha Christie featuring her famous Belgian detective, Hercule Poirot. The novel diverges from Christie's typical whodunit format, focusing instead on international intrigue and conspiracy. In the story, Poirot and his trusted friend Captain Hastings face off against a shadowy group known as The Big Four. This criminal organization consists of four powerful individuals aiming for world domination through manipulation and subversion. Each member of the group is a master in a specific field-finance, science, destruction, and the underworld. The plot unfolds as Poirot connects a series of seemingly unrelated incidents, revealing The Big Four's sinister influence. Unlike Christie's tightly-knit, clue-driven mysteries, this novel has an episodic structure, with Poirot solving smaller cases that eventually link to the overarching conspiracy. Poirot's wit, intellect, and methodical approach lead to the eventual unraveling of the group's plans. Though not one of Christie's most acclaimed works, The Big Four is notable for its more adventurous tone and global stakes. It showcases Poirot's ability to face challenges beyond murder mysteries, diving into espionage and larger conspiracies.