Although Crofts is best remembered for his detective Joseph French, who he introduced in his fifth book, the first book,The Cask, remains one of his most important works, hugely popular at the time, and considered by many critics one of the best and most important mystery books of all time. In a story that codified the "police procedural," the book follows the work of Inspector Burnley, a methodical detective of Scotland Yard, as he investigates the case of a cask that, arriving on the London docks, slips and cracks revealing contents that point to murder.