Clayton asks Sophie what she does to occupy herself while living in Durham. She replies, "I'm working on a new film with Jean and, uh... I come to see your father." Clayton asks if they are working on another documentary, and she responds, "No, no, no, fiction. No more documentaries for us. Kaput." Although the real Sophie Brunet has edited several documentaries since The Staircase for other filmmakers, and she has also worked on numerous other projects with Jean-Xavier de Lestrade, it is true that (as of May 2022) Lestrade and Brunet have not collaborated on another documentary (the projects they have worked on together since have all been scripted, fictional TV or movies).
This episode's title comes from a saying, "nature, red in tooth and claw..." that was in common use from at least the 1830s to describe the savagery of nature and humanity. Its best-known use was probably in Alfred, Lord Tennyson's 1850 poem "In Memoriam A. H. H.": "Who trusted God was love indeed / And love Creation's final law- / Tho' Nature, red in tooth and claw / With ravine, shriek'd against his creed- / Who loved, who suffer'd countless ills, / Who battled for the True, the Just, / Be blown about the desert dust, / Or seal'd within the iron hills?" This same poem contains one of the most famous lines in nineteenth-century English poetry: "I hold it true, whate'er befall; / I feel it, when I sorrow most; / 'Tis better to have loved and lost / Than never to have loved at all."