Third Girl is the third episode of series eleven of Agatha Christie's Poirot. It was broadcast on 28 September 2008. The episode was directed by Dan Reed, with a screenplay by Peter Flannery. It was an adaptation of the Agatha Christie novel of the same name.


Comparison with Original Novel

The main premise of the original novel is retained but otherwise the adaptation diverges significantly from it particularly in the backstories and inter-relationships between the main characters. The changes include:

  • Moving the 1960s setting to the 1930s, in accordance with the other episodes in the series.
  • Omitting the characters of Dr. Stillingfleet and Miss Lemon.
  • Omitting the subterfuge of Mary Restarick posing as Frances Cary. Instead, Mary Restarick is made to be Norma's mother, who committed suicide by slitting her wrists when Norma was a little child.
  • Replacing the character of Louise Charpentier with a new character, Lavinia Seagram, who becomes Norma's nanny. She is murdered in exactly the same way Mary Restarick committed suicide, instead of being pushed out of a window like Louise Charpentier in the novel. The motive of her murder remains the same as Louise's in the novel - she is killed because she threatened to reveal the true identity of Robert Orwell, the man posing as Andrew Restarick.
  • Having Frances Cary become the half-sister to Norma. Norma's old teacher, Miss Battersby, had an affair with Andrew Restarick (Norma's father), and together they bore Frances. When Miss Battersby learned of Robert Orwell and his deception, she told her daughter, who found a way to become Orwell's co-conspirator. Frances tried to get Norma hanged for a crime that she never committed in order to inherit her half-sister's fortune.
  • Having Norma's disoriented state being blamed on the trauma caused by her mother's suicide. She is never given drugs as in the novel. Her fragile mind is manipulated by Frances, who planted a knife in her room before Norma discovered Nanny Seagram's body, and then removed it afterwards. This made Norma believe that she had committed the murder.
  • The character of David Baker being spared at the end, unlike in the novel, in which he was murdered. In the adaptation, he serves as Norma's love interest, whereas in the novel, Norma's love interest is Dr. Stillingfleet.
  • Ariadne Oliver's book Lady Don't Fall Backwards - this is a shout-out to the Hancock's Half Hour TV episode "The Missing Page", in which Tony Hancock tries to find out who committed the murder in a book he'd just read with a missing page (mirrored by the concierge, Alf Renny, who tells Mrs Oliver that he'd read her book four times and still had no idea who did it).


Tropes and themes

Filming Locations

  • Wrotham Park, Hertfordshire - Cross Hedges
  • Witanhurst, Highgate, London - Meadowfield School
  • Alexandra Park, Queensgate, Kensington - Borodene Court


Promotional Videos

Release Dates

Australia - 5 April 2009

Finland - 28 December 2008

Italy - 24 January 2010

Hungary - 6 February 2009

Japan - 15 September 2010

Poland - 30 October 2009

Sweden - 15 September 2008

United Kingdom - 28 September 2008

United States of America - 18 July 2010


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