I have been a huge Agatha Christie/Hercule Poirot fan for many years. Today, I just finished her 25th novel using him as her main character - "Mrs. McGinty's Dead".
Poirot is approached by police Superintendent Spence - whom he has worked with previously. Spence worked to put a man, James Bentley, away for the violent murder of his landlady because of the evidence. James Bentley is now to be put to death for the crime. However, Spence is not convinced that the personality of the man he arrested could ever be brought to the point of murdering another person. Hercule Poirot agrees to look into the killing by moving into the small town of Broadhinny. In classic Christie fashion, Poirot begins to find bits and pieces of non-traditional evidence and psychology that may indicate that the true murderer is still living in the small town. Poirot even comes face to face with his own death while pursuing the truth.