"The Big Four" is a detective novel by Agatha Christie, first published in 1927, featuring the iconic detective Hercule Poirot and his loyal companion, Captain Hastings. It differs from many of Christie's other works in that it is more of a thriller than a traditional whodunit, delving into the realm of international conspiracy.

The story begins when Hercule Poirot's brother arrives in London and dies suddenly. This mysterious event sets Poirot and Hastings on a global pursuit of an enigmatic criminal group known as the "Big Four." These villains are, to the world, highly reputable figures: a multi-millionaire, a brilliant scientist, a Chinese crime lord, and the "Destroyer," a ruthless assassin.

As the novel progresses, Poirot and Hastings are embroiled in a series of daring adventures, navigating intricate plots and death-defying traps. Throughout their pursuit, they encounter a multitude of characters and engage in a cat-and-mouse game with the Big Four.

"The Big Four" showcases Agatha Christie's gift for character creation and her ability to intertwine suspense and mystery. Poirot's brilliance and Hastings' steadfastness shine brightly as they seek to unveil and thwart the criminal organization's dangerous plans. This book offers an exciting deviation from Christie's usual style, embracing elements of espionage and international intrigue while maintaining her characteristic deductive flair.