Henri Cartier-Bresson spent decades walking city streets with a 35mm Leica, waiting for what he called the decisive moment, the fraction of a second when composition, gesture, and meaning align in a single frame. The film traces his path from painting to photography, then through his work for magazines like Life and Vogue, and features interviews with Cartier-Bresson himself alongside friends and colleagues who describe watching him work. It covers his time in the French Resistance during the Second World War and the left-wing politics that shaped which subjects he chose to photograph, from labor strikes to street life. Rather than treating him as a distant master, the film shows him at home with family, offering a rare look at a photographer known for staying out of the frame himself. The result is less a survey of famous images than a portrait of the patience behind them: hours or days spent watching a scene before pressing the shutter once.