Agatha Christie 
Sad Cypress 

An elderly stroke victim dies without having arranged a will…Beautiful young Elinor Carlisle stood serenely in the dock, accused of the murder of Mary Gerrard, her rival in love. The evidence was damning: only Elinor had the motive, the opportunity and the means to administer the fatal poison.Yet, inside the hostile courtroom, only one man still presumed Elinor was innocent until proven guilty: Hercule Poirot was all that stood between Elinor and the gallows…