In October 2019, it was announced Vanessa Kirby and Shia LaBeouf had joined the cast of the film, with Kornél Mundruczó directing from a screenplay by Kata Wéber. Wéber wrote the film based on her own experience losing her child with director Mundruczo, her partner, to an unsuccessful pregnancy.[8] Wéber submitted the script to the Hungarian National Film Fund, but did not get support, later an American producer picked it up.[9]