Ariadne Oliver is a successful detective novelist that appears in two short stories (with Parker Pyne in Parker Pyne Investigates) and seven novels (six of them with Hercule Poirot). The middle-aged writer of detective stories is broad-shouldered and has "rebellious" gray hair, sometimes accentuated with hair extensions. Ariadne Oliver is known for her love for apples and her strong belief in woman's intuition. She is also the creator of the Finnish detective Sven Hjerson, of whom she has a great dislike. The character of Mrs. Oliver is an exaggerated version of Agatha Christie herself (Agatha has shown dislike towards Poirot, her creation, and Agatha was known for eating apples, too). Some of the novels Oliver had written included The Dying Goldfish, The Affair of the Second Goldfish, Death of a Debutante, The Cat it Was Who Died, The Death in the Drain Pipe, The Woman in the Wood (based on her experiences from the Poirot novel Dead Man's Folly), and even her own penned story The Body in the Library. Some of her published articles were The Tendency of the Criminal, Famous Crimes Passionnels, and Murder for Love vs. Murder for Gain.
The first novel in which she appears is the Poirot story Cards on the Table, with Poirot. It is learned in the novel, however, that Poirot and Oliver had already met previously. She assists Poirot and the other detectives in the novel with the investigations necessary to determine the identity of Mr. Shaitana's murderer.
In Mrs. McGinty's Dead, she meets Poirot again in a village where a murder of an elderly lady had taken place (one of my favorite novels--Poirot is great here). Mrs. Oliver invites Poirot to a party to give out prizes for a murder hunt game in Dead Man's Folly, only to find a real dead body. She pairs up with Poirot again in Third Girl to search for a missing girl who might have committed a murder. (Oliver is great fun in this one.)
Ariadne has been invited to a Hallowe'en Party for young people going to school, to then find a girl murdered there; she ends up enlisting Poirot to help her discover the murderer's identity. In her final recorded case with the Belgian sleuth (Elephants Can Remember), she aids Poirot in uncovering a mysterious murder-suicide of the parents of her goddaughter.
The Pale Horse is the only novel in which Poirot doesn't appear with Ariadne. The story begins with the murder of a priest caused by a vital secret he held. The story centers on a young man's attempt to solve the murder; Mrs. Oliver helps him, whose cousin was known to Oliver in the novel Cards on the Table. Together the young man and the police uncover a plot connected with the secretive Pale Horse Inn. (In my opinion, The Pale Horse is one of the very best of Agatha Christie. This book, too, ranks highly among the later Christies.)
On screen, two actresses have portrayed Mrs. Oliver. The American actress Jean Stapleton starred as Ariadne Oliver in a television adaptation of Dead Man's Folly in 1986, with Peter Ustinov as Poirot. More recently, in 2005's Cards on the Table with David Suchet as Poirot, Zoe Wanamaker appeared as Mrs. Oliver. What is exciting is that Wanamaker returned in two more appearances as Oliver in Mrs. McGinty's Dead and Third Girl, both in 2008.