The principle of the film l'Ébranlement is twofold, based on the visual approximation of two distant terms (fencing and fireworks) and on a principle of expenditure (the possible engendering of one by the other). Images of fireworks are edited in echo to shots of a fencing duel, situated in a perforated architecture, with arcades (the Vieille Charité, in Marseille), which multiplies the incessant passages from shadow to light. At the moment of the clash (the point of the foil touching the opponent's body), the fireworks unfold as if the contact was established - an explosion, an epidemic mode of contamination by successive stings, point by point. The touch of the foil answers the blaze of the sky. As soon as the sky darkens, after the last spikes of light are extinguished, the fencing duel can be resumed, like a carillon or an automatic game. The attack is a flash of lightning that sets the collar on fire.