Hercule Poirot doesn't need all his detective skillsto realize something is troubling his secretary, MissLemon--she has made three mistakes in a simpleletter. It seems an outbreak of kleptomania at thestudent hostel in which her sister works isdistracting his usually efficient assistant.Deciding that desperate times call for desperatemeasures, the great detective agrees to investigate.Unknown to Poirot, however, desperation isa motive he shares with a killer. . . .