# Katherine Grey — The Mystery of the Blue Train character guide > Katherine Grey in The Mystery of the Blue Train by Agatha Christie. **Role:** major **Also known as:** Miss Grey, Miss Katherine Grey, Katherine, Mademoiselle Katherine **First appearance:** 0004-iii-heart-of-fire ## Snapshot A serene, sharp-eyed former companion who inherits a fortune and a dead woman's last conversation, making her both witness and target. ## Who they are Katherine spent a decade managing a difficult old lady in Little Crampton, and she carries that hard-won composure into a sudden inheritance and a first-class ticket to the Riviera. On the train she listens to Ruth Kettering's confidences about a lover and a decision, never guessing how much those words will matter. Her quiet grey eyes and unshakeable good sense draw both Derek Kettering and Van Aldin's secretary toward her. She is the reader's grounded centre in a world of wealth, suspicion, and restless men. ## Relationships ### [Hercule Poirot](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/hercule_poirot) _friendship_ Poirot respects Katherine's intelligence and integrity, forming a trusting alliance during the investigation. ### [Derek Kettering](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/derek_kettering) _romantic_ Derek is drawn to Katherine's calm and genuine nature, developing romantic interest after his wife's death. ### [Ruth Kettering](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/ruth_kettering) _social_ Katherine meets Ruth on the train and has polite but brief interactions before Ruth's murder. ### [Lenox Tamplin](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/lenox_tamplin) _friendship_ Katherine and Lenox become friendly companions during Katherine's stay at the Tamplin villa. ### [Lady Tamplin](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/lady_tamplin) _social_ Katherine is a guest of Lady Tamplin, who treats her with superficial hospitality. ### [Comte de la Roche](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/comte_de_la_roche) _psychological_ The Comte attempts to charm and manipulate Katherine for his own ends. ### [Major Knighton](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/major_knighton) _friendship_ Katherine and Knighton share a cordial, supportive relationship as they assist Poirot. ### [Hercule Poirot](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/hercule_poirot) _friendship_ Poirot respects Katherine's intelligence and integrity, forming a trusting alliance during the investigation. ### [Lenox Tamplin](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/lenox_tamplin) _friendship_ Katherine and Lenox become friendly companions during Katherine's stay at the Tamplin villa. ### [Hercule Poirot](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/hercule_poirot) _friendship_ Poirot respects Katherine's intelligence and integrity, forming a trusting alliance during the investigation. ### [Ruth Kettering](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/ruth_kettering) _social_ Katherine meets Ruth on the train and has polite but brief interactions before Ruth's murder. ### [Derek Kettering](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/derek_kettering) _romantic_ Derek is drawn to Katherine's calm and genuine nature, developing romantic interest after his wife's death. ## In the story ### [The Mystery of the Blue Train](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/the-mystery-of-the-blue-train) A fellow passenger who becomes an unwitting witness to the events on the train. ### [VI: Mirelle](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/vi-mirelle) Briefly encountered by Derek in the corridor; he later muses on her as 'Portrait of a lady with grey eyes.' ### [Letters](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/vii-letters) Receives letters about her inheritance, reflects on her past as a companion, and decides to travel and buy new clothes. ### [Lady Tamplin Writes a Letter](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/viii-lady-tamplin-writes-a-letter) Visits lawyers, arranges a sum for Mrs. Harfield's relatives, shops for clothes, and books a trip to the Riviera after receiving Lady Tamplin's letter. ### [An Offer Refused](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/ix-an-offer-refused) Katherine is seen at Thomas Cook & Sons booking a ticket on the Blue Train to Nice, coincidentally on the same day as Derek. ### [X: On the Blue Train](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/x-on-the-blue-train) Travels on the Blue Train; listens to Ruth's confidences and later dines with Hercule Poirot. ### [XI: Murder](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xi-murder) Wakes to sunshine, identifies the murdered woman, and agrees to help Poirot investigate. ### [At the Villa Marguerite](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xii-at-the-villa-marguerite) Katherine is the guest at Villa Marguerite, recounting the murder to Lady Tamplin and her family. She feels uncomfortable with Lady Tamplin's schemes and later remembers seeing a man enter Ruth's compartment, but decides not to tell the police. ### [XVIII: Derek Lunches](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xviii-derek-lunches) Katherine arrives at the Negresco and is invited by Derek to have lunch with him. ### [Katherine Makes a Friend](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xx-katherine-makes-a-friend) Sits on the terrace with Lenox, discusses Derek Kettering, receives a phone call from Poirot, meets with Van Aldin to recount her conversation with Ruth. ### [At the Tennis](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xxi-at-the-tennis) Attends the tennis match with Knighton and Poirot; is questioned about the cigarette case. ### [XXIV: Poirot Gives Advice](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xxiv-poirot-gives-advice) Arrives in a car outside the hotel; Derek speaks with her earnestly before she drives off. ### [A Warning](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xxvi-a-warning) Katherine is the focal point of the chapter, receiving warnings and declarations from both Derek Kettering and Major Knighton, and sensing the presence of Ruth Kettering. ### [Interview with Mirelle](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xxvii-interview-with-mirelle) Mentioned as having confirmed seeing Derek Kettering go into his wife's compartment before the train reached Lyons. ### [A Letter from Home](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xxix-a-letter-from-home) Reads a letter from Miss Viner and feels a longing for home; later lunches with Poirot and Lenox. ### [Miss Viner Gives Judgment](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xxx-miss-viner-gives-judgment) Katherine is staying with Miss Viner, reading letters from Poirot and Knighton, and arranging Knighton's visit. ### [XXXII: Katherine and Poirot Compare Notes](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xxxii-katherine-and-poirot-compare-notes) Meets Poirot at the Savoy, shares a newspaper cutting, and expresses emotional urgency for the case to be resolved. ### [Explanations](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xxxv-explanations) Mentioned as having sensed Ruth's presence and acted on her intuition about Knighton's guilt. ### [By the Sea](https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/chapters/xxxvi-by-the-sea) Mentioned as reserved and untrusting; Lenox had wrongly thought she cared for Knighton. ## Links - HTML: https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters/katherine_grey - Book: https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se - All characters: https://www.betterreads.dev/discover/the_mystery_of_the_blue_train_se/characters