In the novel Sparkling Cyanide, Betty Archdale was a former parlourmaid at the Barton household. Lucilla Drake had found her impertinent and careless. Mrs Drake also claims that she had broken six glasses of the finest type at the same time.
At the time of Rosemary Barton’s ‘suicide’, Betty had suspicions about it being murder. She brought this up to Mrs Drake, saying that she hoped that in her next place, she would not be in the kind of house where "people got bumped off". Mrs Drake found this comment insolent.
In Betty's reference, Mrs Drake wrote that Betty thoroughly understands her duties as a parlourmaid, and that she is sober and honest. However, she also writes that Betty is "inclined to have too many breakages", and that her manner is not always respectful.
After leaving her job with the Bartons, Betty is employed by a Mrs Rees-Talbot.
Colonel Race calls on Mrs Rees-Talbot when he wants to talk to Betty. Mrs Rees-Talbot tells him that Betty is "an artful dodger" and has the "close-to-the-door-when-there's-anything-interesting-going on technique very highly developed".
Betty tells Colonel Race that she had overheard something which made her think that Rosemary's death was not suicide. She says that the door was not closed, and she would never go and listen at a door, but she had overheard Rosemary talking to Anthony Browne, as they were speaking quite loudly. Rosemary had said that Anthony Browne was not his real name, and Anthony had said something about carving up her face, and that if she did not do what he told her, he would "bump her off".
Colonel Race suggests that Betty wrote anonymous letters to George Barton, telling him that Rosemary had not committed suicide, but had been killed. However, Betty repeatedly denies this, "not vehemently or uneasily, but soberly and without undue protestation".
Betty tells Colonel Race that Rosemary had mentioned that Anthony's real name was Tony. Betty cannot remember the last name, but tells Colonel Race that it begins with M, sounds foreign, and reminded her of the cherry jam which cook had been making.