In the short story The Girdle of Hyppolita, Mrs Elliot is a passenger on the same train from London to Paris as the one from which the English schoolgirl Winnie King disappeared. She had been travelling with her husband James and they had occupied a compartment in the same carriage as that Winnie had disappeared from. Detective Inspector Hearn considered her husband a plausible suspect. As for Mrs Elliot, she was, he told Poirot, "a flashy piece of goods".
Poirot would later conclude that Mrs Elliot was a "quick change artiste" who impersonated Winnie King at the time of departure and then changed back to her own self just after Amiens. It was all part of an elaborate plan by a gang of art thieves to get a stolen painting across borders. According to Poirot, James Elliot's passport did include a wife, but it is not clear if the woman on the train was in fact the real Mrs Elliot or just a fellow gang member. Her real name is not given.