Hastings is at a friend's house with several other people when the talk turns to flats and houses. Mrs Robinson tells the party how she and her husband have managed to obtain a flat in Knightsbridge for a very attractive price. Poirot is interested in this strange event and starts to investigate. The porter at the flat tells them that the Robinsons have been there for six months, despite Mrs Robinson telling Hastings they had only just obtained the...