When you've been denied justice... you are incomplete. It feels that God has abandoned you in a stark place. I asked God... I think we all did... what we should do. And He said, "Do what is right." And I thought if I did, it would make me complete again. (Poirot: And are you?) But I did what was right.
~ Mary Debenham to Poirot (2010)
Not now. Not now. When it's all over. When it's behind us. Then...
~ Mary Debenham to Colonel John Arbuthnot, also her most famous quote

Mary Hermione Debenham is a major protagonist in Agatha Christie's 1934 Hercule Poirot novel, Murder on the Orient Express, and its adaptations. She is one of the twelve culprits of the story that killed Lanfranco Cassetti.

She was portrayed by various actresses including Vanessa Redgrave in 1974, Natasha Wightman in 2001, Jessica Chastain in 2010, and Daisy Ridley in 2017.


Being one of the closest familiars to the Armstrong Family before its tragedy, Ms. Debenham was a professional governor to Countess Helena Andrenyi and formerly a tutor to the late Daisy Armstrong, and a personal secretary to the late Sonia Armstrong. In the 2010 film, she had her arm broken and paralyzed by Cassetti's thug. She participated in his murder and was one of the twelve who stabbed him to death in his sleep.

After the deaths of Daisy, Mary became a governess in Istanbul teaching two children. She was in a relationship with Colonel John Arbuthnot, the closest friend of the late Colonel Armstrong, who also participate the murder to avenge his friends. Their brief interaction whilst pretending as strangers was spotted by Poirot, and it later became a factor to solve Casetti's murder. She was eventually spared alongside other culprits because of the sympathetic circumstances behind the murder.

On board the Orient Express, Mary occupied berth No. 11, sharing a second-class compartment on the Calais coach with Greta Ohlsson who was in the lower berth, No. 10.


Agatha Christie's signature.png Heroes

Main Detectives
Hercule Poirot | Jane Marple
Secondary Detectives
Parker Pyne | Mr. Quin | Tommy and Tuppence Bresford
Amateur Detectives
Colonel Johnnie Race | Superintendent Battle | Bobby Jones | Frances Derwent | Arthur Calgary | Reniseb | Charles Hayward | Mark Easterbrook

Righteous Culprits
Mary Debenham | Princess Natalia Dragomiroff | Hector MacQueen | Edward Masterman | Colonel John Arbuthnot | Linda Arden | Count Rudolph Andrenyi | Countess Helena Andrenyi | Greta Ohlsson | Pierre Michel | Antonio Foscarelli | Hildegarde Schmidt | Cyrus Hardman | Edith de Haviland | Hercule Poirot
Short Stories
Madame Déroulard | Ronnie Oglander

Supporters, Victims & Others
Captain Arthur Hastings | Inspector Japp | Felicity Lemon | Ariadne Oliver | George the Butler | Superintendent Spence | Colonel Johnnie Race | Superintendent Battle | Countess Vera Rosakoff | Raymond West | Joyce Lemprière
Victims & Attempted Victims
Alexander Bonaparte Cust | Miranda Butler | Mrs. Otterbourne | Pilar Estravados | Olga Seminoff
Bella Duveen | Colonel Carbury | Dr. Stavros Constantine | Dr. Gerard | Dulcie Duveen | Ginerva Boynton | Hori | Judith Butler | Lydia Lee | Miss Bulstrode | Monsieur Bouc | Monsieur Giraud | Nadine Boynton | Rosalie Otterbourne | Sarah King | Sophia Leonides | Stephen Farr | Tim Allerton | Valerie Saintclair | Virginie Mesnard

Adaptational, Homage & Non-canonical
Benoit Blanc | Marta Carbera | Linda Drysdale

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