In the novel A Caribbean Mystery, Esther Walters (later Anderson) was the secretary of Mr Rafiel. She travelled with him on his vacation to St Honoré. Her late husband was a wastrel and did little to support his family. He stepped in front of a bus while drunk and was killed. Esther was left to look after a daughter. Mr Rafiel subsequently made himself responsible for Esther's daughter's schooling and paid for her to be educated at a boarding school.
Tim Kendal had planned to marry her after his wife's death, since he found out that Esther was going to inherit a large sum of money from Mr Rafiel who could be expected to die soon. Thus Esther was the motive behind the subsequent murder of Molly although nothing in the book suggests that Esther was complicit in or even knew about Tim's plans.
Esther appeared again in the novel Nemesis. Here she had been married some four or five months to an engineer, a Mr Anderson, and moved to Winslow Lodge in Alton in Hampshire, near Haslemere and some twenty five miles from St. Mary Mead.
When Miss Marple received a posthumous commission from Jason Rafiel to investigate an unspecified injustice, she first wanted to meet Esther whom she thought might be able to give her some background. Miss Marple learnt Esther's latest addres from Joan Prescott and then contrived to meet Esther apparently by coincidence outside a supermarket near Alton and got herself invited to tea. However Esther did not reveal very much, either because she didn't know or didn't want to say. All Esther told Miss Marple was that Mr Rafiel had two daughters and a son who he never talked about. There was nothing troubling him during the last months of his life. In any case, Mr Rafiel seldom revealed his personal thoughts--his only preoccupation was business. After meeting Esther, Miss Marple concluded that whatever injustice Mr Rafiel wanted investigated, it had nothing to do with Esther. Indeed, Mr Rafiel had left Esther fifty thousand pounds upon his death, just as he had intended to at the time of A Caribbean Mystery and he had not changed his mind despite the events on St Honoré. This plan of his was not known to Esther at that time (although others such as Tim Kendal and Jackson knew about it). Esther told Miss Marple that the legacy was a pleasant surprise and she intended to use it to live a life of leisure and indulge in luxuries for a while.
In the 1983 Warner Bros adaptation of A Caribbean Mystery, her name is "Ruth Walter". Here she is a trained nurse. She introduces herself as Mr Rafiel's "nurse, secretary and entertainment manager". The part of Ruth Walter is played by Swoosie Kurtz. In this adaptation, she is the one who makes the observation to Miss Marple that Molly didn't take enough of the sleeping pills to cause any harm. "She had it timed right to the minute", almost as if she had staged the event. Dr Grahame confirms this puzzling observation. She is also the one who fills in Miss Marple about Molly Kendal's family background.
In the BBC 1989 adaptation of A Caribbean Mystery, Esther Walters is portrayed by Barbara Barnes. In this adaptation, it is likely that Esther was complicit in the murder of Molly. Certainly there was an active affair between her and Tim Kendal. In one of the last scenes where Tim is caught red-handed trying to poison Molly, Esther declares her love for Tim, causing Tim to tell her to shut up because her words would get him hanged.
In the 2013 ITV adaptation of A Caribbean Mystery, Esther Walters is portrayed by Montserrat Lombard.