Agatha Christie also created other detective characters.
Thomas Beresford and his wife, who appeared in four novels and an anthology of short tales released between 1922 and 1974, were amateur detectives created by Christie in addition to Poirot and Marple. Her other minions, the Beresfords, who were introduced in The Secret Adversary when they were only in their twenties, were permitted to grow older alongside their maker. She gives their stories a "dash and energy" that isn't admired by reviewers, treating them with more compassion. Postern of Fate, their last adventure, is Christie's final book.
The "easily most unconventional" of Christie's fictional detectives is Harley Quin. Quin, a semi-supernatural character, has always collaborated with an elderly man known as Satterthwaite, who was inspired by Christie's love of characters from the Harlequinade series. 14 short stories featured the duo, 12 of which were gathered in Mr. Quin's Mystery in 1930. These tales are "a touching, wonderful discovery of a fairy tale, a natural result of Agatha's great imagination," according to Mallowan. Satterthwaite also made an appearance in the Poirot-starring short story "Dead Man's Mirror" in the novel Three Act Tragedy.
Parker Pyne, a retired civil worker who assists the unfortunate in an unorthodox way, is one of her less well-known characters. Parker Pyne Investigates (1934), a collection of 12 short stories that introduced him, is best known for "The Disgruntled Soldier Case," which featured Ariadne Oliver, "an amusing and caustic self-portrait by Agatha Christie." Seven novels featuring Oliver in the decades that followed had her in most of them as Poirot's main supporter.
