Cyanide: Achille, 13, awaits, full of hope, the release from prison of his father, unknown and fantasized. His dream of living as a threesome, like a real family, will be seriously undermined by a mother exhausted from waiting and this father who is unsuitable and made irresponsible by so many years of incarceration. Will this vulnerable person with a flamboyant past be able to keep the promise he made to his son to never live apart from him again?