When a pacifist and humanitarian speaker, called "the Deputy", is attacked by far-right extremist thugs on his way to a rally, an unidentified man joins the rally organizers to help get him to safety and then justifies his presence:
"Qu'est que toi?" ["And you?"]
"Moi, suis maçon." ["I'm a mason."] [00:24:50]
Later, when the Deputy is assassinated, the mason pursues the murderers and is himself attacked. A minor character, he is not seen again until he is testifying to a judge near the end of the film. In contrast, in the novel Z, one of the judges is accused of being a freemason, and therefore protective of the general responsible for ordering the assassination. Based on the assassination of anti-fascist Greek politician and peace activist, Gregoris Lambrakis (1912-1963), in real-life one of the rally organizers pursued Lambrakis' assassins and was responsible for their arrest.
In context, it is unclear if the character in the film is a freemason or works as a stonemason, although justifying his presence backstage at a peace rally by giving his occupation doesn't appear reasonable.
Z (1969) Directed by Costa-Gavras, written by Vassilis Vassilikos (novel) Jorge Semprún. Yves Montand, Irene Papas, Jean-Louis Trintignant, Jacques Perrin, Charles Denner, François Périer, Pierre Dux, Georges Géret, Bernard Fresson, Marcel Bozzuffi, Julien Guiomar, Magali Noël, Renato Salvatori, Habib Reda, Clotilde Joano. 127 min, Algeria / France, French. Eastmancolor, Mono. Visa de Contrôle Cinámatographique No. 34.695.