In the novel The Body in the Library, Josephine “Josie” Turner is a dance and bridge hostess at the Majestic in Danemouth. She is a cousin of Ruby Keene. After injuring her ankle, she brought Josie brought her cousin in to dance at the Majestic in her place.
Josie is described as "a good-looking young woman of perhaps nearer thirty than twenty, her looks depending more on skilful grooming than actual features".
After the murder of Ruby Keene, Josie was not considered as a prime suspect because it would appear that she had much to lose with the death of her cousin who was about to be adopted by the wealthy Conway Jefferson. However research by Miss Marple at Somerset House revealed that Josie had secretly married Mark Gaskell and stood to lose a large sum of money as what would go to Ruby would otherwise have gone to Mark and Adelaide Jefferson who were the nearest living relatives of Conway.
On the night of the murder, Ruby had been drugged. Miss Marple suggested after-dinner coffee as a probable vehicle for the drug. Ruby had been told to change, and go to Josie's room and wait. When Josie went upstairs, she killed Ruby.
Conway Jefferson told Mark and Adelaide that he was making a new will, leaving the money that would have gone to Ruby to endow a hostel for young dancers in London. The night before he was due to see his lawyer, Josie entered his room, and attempted to inject him with digitalin. She had also loosened one of the stone balls on the balcony outside, and was going to let it crash down, so that Conway's death would look like a case of heart failure due to the shock of a sudden noise. However, she was caught in the act by the police.
In the ITV 2004 adaptation of the novel (Episode 1, Season 1 of Agatha Christie's Marple), Josie is played by Mary Stockley. Her portrayal is changed substantially. Here she is not secretly married to Mark Gaskell but has a love relationship with Adelaide Jefferson.