Cards on the Table (1936) is a detective novel by Agatha Christie.
Warning: Wikipedia contains spoilers.
Hercule Poirot is invited to a dinner party at Mr Shaitana's house and after dinner the eight guests settle down for a game of bridge. The two games are set up so that four guests play in one room and the other four play in an adjoining room which could only be accessed from the first room. Poirot joins Mrs Ariadne Oliver (an author of crime fiction books), Superintendent Battle (a policeman) and a general for the game in the inner room. Mr Shaitana, the host, sits with the other group of four in the outer room away from the poker table by a fire place. At the end of the night Mr Shaitana is found dead in his chair by the fire. It becomes obvious that he must have been killed by one of the four players in the room (Major Despard, Dr Roberts, Mrs Lorrimer and Anne Meredith), all of whom have murdered - successfully - before. Further investigation shows that the murder must have taken place when the murderer was the dummy.Plot
