On nights when her husband is absent, a forbidden secret unfolds between them. The son gives in to temptation and takes his drunken stepmother, surrendering to overwhelming pleasure. That night, though confused, she feels her heart stir as she becomes aware of her growing connection with her stepson. Grieving the loss of her beloved husband, Mariko Yoshinaga begins to lean emotionally on her stepson, and their taboo intimacy deepens gradually. Their relationship escalates, giving birth to a forbidden love. On these secret nights, their fates intertwine.