This is the 15th Hercule Poirot full length novel that was first published in 1937. It is a very clever mystery featuring Poirot right from the start. There's lots of clues and hints for the reader to indulge in. There's two other subplots that will keep the reader on their toes. The story moves very quickly so the reader must keep up with the details of each event in order to sort out the significance behind them. This mystery is one of Christie's best. I would rank this mystery slightly behind The Murder of Roger Ackroyd.