Miss Hartnell is described as "weather-beaten and jolly and much dreaded by the poor", and she speaks in "a loud, hearty voice".
In The Murder at the Vicarage, Miss Marple mentions a case that occurred some time before the events of the novel. Miss Hartnell had left her opal pin in a frilled blouse, and sent it to the laundry. The woman who took it did not want it, but she put it in another woman's house and told the police that she had seen her take it, purely out of spite.
In The Mirror Crack'd from Side to Side, Miss Hartnell is described as "fighting progress to the last gasp". She dislikes the supermarket that now stands at the end of the village street, where Mr Toms had once had his basket shop. Miss Hartnell complains about being expected to take a basket and go around looking for things herself, which sometimes takes a quarter of an hour. She also says that things in the supermarket are usually sold in inconvenient sizes, either too much or too little, and that there is a long queue waiting to pay as you go out.
In Tape-Measure Murder, Miss Hartnell finds Miss Politt knocking on the door of Laburnum Cottage. Miss Politt asks her if she knows if Mrs Spenlow is out. Miss Hartnell knocks, and then looks through the window. She sees Mrs Spenlow lying dead on the hearthrug, and goes to fetch Constable Palk. She also tells people about the incident, includiecause she ng her suspicions of Mr Spenlow, because she feels it is not natural for a man to hear that his wife is dead, and to show no emotion.
- The Murder at the Vicarage (1930)
- The Body in the Library (1942)
- The Case of the Perfect Maid (1942)
- Tape-Measure Murder (1942)
- The Mirror Crack'd from Side to Side (1963)