The original book features Poirot taking on twelve cases (12 short stories) each one referencing Greek mythology. The TV adaptation is a combination of some of those stories into a single location. The central plot is "The Erymanthian Boar" which takes place in a Swiss mountain-top hotel as Poirot searches for master-criminal Marrascaud. In "The Arcadian Deer" Poirot is asked by a car mechanic to locate the maid of a Russian ballerina. "The Stymphalean Birds" features a man trying to help a woman in an abusive marriage. "The Girdle of Hippolyta" is about stolen paintings. While "The Capture of Cerberus" has Poirot reunited with Countess Vera Rossakoff.
The title is fitting for both the book and this episode as Hercule's name is French for Hercules, who performed 12 labours in Greek myth.
The character name Lucinda Le Mesurier is a reference to "The Lemesurier Inheritance" a Poirot short story (not adapted for the series) about a family-curse that claims the life of first-born sons in the Lemesurier family.
Orla Brady replaces Kika Markham who previously portrayed Countess Rossakoff in The Double Clue (1991). The countess also appears in The Big Four, but her character was omitted from the episode, The Big Four (2013), which is only loosely based on the novel.
Patrick Ryecart who plays "Sir Anthony Morgan" was in an earlier episode, Dumb Witness (1996), as "Charles".