Getting Happy with Parker Pyne: The Gate of Baghdad by Agatha Christie

Parker Pyne is still abroad, spreading his statistician-acquired cynical know-how the same way his forebears spread smallpox, this time on a "Pullman coach" across the desert from Damascus to Baghdad in which a sock may or may not have been used to murder someone. Where's Rob Kardashian when you need him? Fortunately, he's right here!