In the short story The Third Floor Flat, Patricia Garnett was a young woman who lived on the fourth floor of the building Poirot was living in. Coming back from dinner and the theatre with some friends, she found that she had mislaid her keys. Two of her party, Donovan Bailey and Jimmy Faulkener attempted to get into the flat by the coal lift. They got into the third floor flat instead and discovered the dead body of Ernestine Grant.
Although she played a central role in the story, there is very little description of her. It is suggested that she was impulsive and forgetful. She had mislaid her keys on other occasions and she periodically neglected to bolt the door of her coal lift. She was beautiful, had blue eyes and played the piano. She cooked omelettes well. Poirot enjoyed and praised her omelettes. At the end of the story, Poirot attempted to matchmake her with Jimmy Faulkener.
Patricia was played by Suzanne Burden in the film adaptation of The Third Floor Flat in Series 3 of ITV's Agatha Christie's Poirot. There she was renamed "Patricia Matthews" but the portrayal is otherwise faithful to the original including her skill with omelettes and being paired off with Jimmy Faulkner.