In the short story The Under Dog, Miss Langdon is the manageress of the Golf Hotel at Abbots Cross, near Mon Repos, the residence of the Astwell family. Poirot spoke to her in the course of his investigation into the death of Sir Reuben Astwell. Miss Langdon knew the movements of her guests and was certain that none of them had gone out for a walk after dinner on the night of his death. There was nowhere to go to. For her, the attractions of Abbots Cross was golf and nothing but golf.
Miss Langdon is not featured in the film adaptation of the story in Series 5 of ITV's Agatha Christie's Poirot, although Poirot and Hastings stayed at the hotel.