In the novel Hickory Dickory Dock, Elizabeth Johnston is a Jamaican resident at boarding house/hostel run by Mrs Nicoletis at 26 Hickory Road who was studying law. At the beginning of the story, along with a string of mysterious thefts and disappearances of property, someone had splashed green ink all over a set of Elizabeth's notes which were the result of a few months of hard study.
To Mrs Hubbard and others in the hostel, this was strange. As Sally Finch, an American resident at the hostel said, Elizabeth was quiet and kept to herself but was generally very well-liked. Elizabeth was affectionately known as “black Bess” by the other residents in the hostel. Mrs Hubbard described Elizabeth as "a hard worker, ambitious, who kept very much to herself. She had always seemed particularly well balanced and competent." Mrs Hubbard considered Elizabeth as one of the most satisfactory students in the hostel. Elizabeth did, however, have a dislike for the American student Sally Finch. Neither Poirot nor Inspector Sharpe could understand why until a detailed search of the hostel premises uncovered the fact that she carried a party card as a member of the communist party.
Elizabeth did contribute one important lead to the investigation into the murder of Celia Austin. She told the police that on the evening of the day she died, Celia had come to her and told her in a rather disjointed manner that she was not responsible for some of the thefts and strange events at the hostel although she was responsible for others. She was not responsible for cutting up the rucksack or stealing the lightbulbs. Celia seemed to imply that she knew who had done it but it was just that she did not understand why. She also wondered if it had anything to do with "the passport", implying that someone had a forged passport. Celia left Elizabeth the cryptic remark that by the next day she would know more about it.
Elizabeth is not featured any of the film adaptations of the novel.