Fire and Ice

Le Combat dans l'île is a 1962 French drama film directed by Alain Cavalier and starring Romy Schneider and Jean-Louis Trintignant. Set in the context of the campaign of bombings and assassinations by the Organisation de l'armée secrète, it tells the story of an austere young man who is corrupted by the lure of terrorism and of his more sympathetic wife, who finds both independence and a more worthwhile partner.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.