Philippe Haïm started working on this film by writing down everything he could about the D.G.S.E. (the French secret service) and the challenges and threats the agency seems to receive. He then proceeded to write three drafts of the script with the input of several consultants, after which co-writer Julien Sibony came in, and later Natalie Carter. Not knowing anything about the world of espionage and counter-terrorism, Sibony was able to see the script's weaknesses, such as when it was unclear for the uninitiated, and Carter was essential to develop Vahina Giocante's character Diane. In the end, the 18th draft was the shooting script, even though several changes were made while filming and even during the editing process.
In preparation for her role, Vahina Giocante gained a basic knowledge of Arabic and developed a specific corporal demeanor for her character, who, according to director/co-writer Philippe Haïm, ages 10 years in the space of a few months.