In a cramped attic, a French brother and sister, bored and restless, find themselves drawn to each other. The sister, a young beauty with a mischievous glint in her eye, suggests a game of truth or dare. As the game heats up, dares become more risqué, culminating in a passionate, forbidden kiss. They struggle with their conscience but the taboo excitement proves too much to resist, leading to a heated, French-language exchange of desires.