Hercule Poirot's loyal secretary.
Poirot refers to her as his "perfect machine" until one day when she makes three typing mistakes in a simple letter.
Her appearances are usually very brief and have no impact to the story. She is "sublimely incurious." She has a little room in Poirot's office at Whitehaven Mansions. She doesn't like to "play detective"--she would rather be completing her secretarial tasks.
"Miss Lemon, always efficient, had preceded him to the street and was waiting by a taxi. She asked no questions and displayed no curiousity. She did not tell Poirot how she would occupy her time while he was away. She did not need to tell him. She always knew what she was going to do and she was always right in what she did." --Third Girl