In the novel One, Two, Buckle My Shoe, Miss Gladys Nevill was the twenty-eight year old secretary of the dentist Henry Morley, who left her one hundred pounds after his death. She was described as 'a tall, fair, somewhat anaemic girl'.
One morning Gladys did not show up at work because apparently, her aunt had had a stroke and therefore she needed to go down to Somerset. Morley discussed of this with his sister Georgina, which believed the story because Gladys was 'an intelligent girl' which was 'keen on her work too'. He agreed but remarked that this was before she had started to hang out with her new boyfriend Frank Carter, who could have persuaded her to take a day off.
It later turns out that Miss Nevill's aunt was fine and still alive, and that she was called away at the time her employer was killed. She believed that to be a “wicked practical joke”. As a result, she threw the telegram away and could not show it to Inspector Japp. She claimed it only said: 'Your aunt had a stroke last night. Please come at once'.
At the inquest of Henry Morley's death, it was believed that he had killed himself after accidentally giving a patient an overdose. Nevill came to Poirot and told him that the verdict was wrong, because it was not possible that the dentist could have accidentally given too much sedative. However she didn't say it at the inquest because it might have been believed that Morley killed his patient purposefully.
Some weeks before the events in the novel, Carter had lost his job as an insurance clerk and Gladys let him spend some of her savings.