In the confines of their family home, siblings Lucy and Max navigate their forbidden desires. Lucy, a devout Catholic, struggles with her lust for her brother, while Max, fueled by teenage hormones, can't help but crave his sister. One evening, Lucy, clad in a modest nightdress, finds Max masturbating in the bathroom. Instead of recoiling, she's drawn to him, her own desires igniting. She joins him, their bodies entwined as they pleasure each other, their shared sin both exhilarating and shameful.