Jane Mason

In the short story The Plymouth Express, Jane Mason was the maid of Flossie Carrington. In the course of investigating the murder of Mrs Carrington, Poirot unmasked Mason as Gracie Kidd, the accomplice of a notorious jewel thief Red Narky. The two of them had acted together in the murder of Mrs Carrington and the theft of her jewels. Mason's role in this was to dress up as her employer and travel further down the line, drawing attention to herself, thus creating the impression that the murder took place later than it actually was, and creating an alibi for herself and her accomplice.

Poirot became suspicious of her when she put too much stress on describing her employer's brightly coloured and noticeable clothing. As the maid, she had some influence on the clothes her mistress wore and she probably chose a bright electric blue so that people who saw her impersonating Mrs Carrington would remember.

Portrayals
Jane Mason was played by Marion Bailey in the film adaptation of The Plymouth Express in Series 3 of ITV's Agatha Christie's Poirot. Her accomplice in the adaptation was not Red Narky but a different character named McKenzie.

In NHK's anime adaptation The Plymouth Express, the name of the character is changed from Jane Mason to "Louise" but her real name-in-crime is still Gracie Kidd. The voice actress behind the character is not credited.