We're doing a classic Hercule Poirot mystery novel from the master of the art, Agatha Christie. This book's got it all - a man with a fortune who won't share his cash, suspicious behaviour from close family members, potentially disgusting behaviour on the part of a butler, the world's worst attempt at going incognito, and a very strange way of deciding who is trustworthy (featuring the Daily Mail). Spoilers - Ackroyd isn't long for this earth. But we're in it until the shocking revelation in a few weeks! For now, let us know who you think dunnit at firstname.lastname@example.org, or on Twitter via @sharkliveroil.