Agatha Christie's Poirot S01 E09 The King of Clubs

Lovely young actress Valerie St Clair, engaged to marry Prince Paul of Maurania, is the only witness to the murder of Henry Reedburn, a shady and overbearing producer. Prince Paul appeals to Poirot to save Valerie from police suspicion, and the great detective finds he has a conundrum to ponder on, 'When is a murder not a murder?'