The King of Clubs By Agatha Christie : A Hercule Poirot Mystery

Hercule Poirot is asked by Prince Paul of Maurania to come to the aide of his fiancé who seems to be involved in the murder of Henry Reedburn in some way. It has greatly distressed her. She is the famous dancer Valerie Saintclair. The only other witnesses seem to be a family of four who were playing bridge at home near an open window through which she staggered in, crying "Murder!"