"The Big Four," is the first mystery in which Poirot is in action rather than thinking deeply in a chair. Poirot hears rumors about something termed, "the Big Four." Throughout the book, he investigates this with his devoted friend Captain Hastings. Gradually he becomes involved in a mission to save the world, which Agatha Christie writes very convincingly. Hercule Poirot and Captain Hastings, also the narrator, go through many experiences as the Queen of Crime proves that Poirot is capable of the most confusing puzzles, and even the world's most potentially dangerous criminals. Her style of writing, in this book, is like a series of short stories having to do with one another---each chapter introducing a puzzle which Poirot must solve, and entering a new one in the next. Interesting as the flow and style of this book is I have rated "the Big Four" with 4 stars due to the slightly disappointing conclusion. All in all, this book is another classic by Agatha Christie. Fairly fast-paced, one is breathless each page they turn. Not her best book, but worth the time and money.