Child abuse is arguably one of the cruelest of crimes. But just as despicable, if not worse, is the all-too common tendency of society to turn a blind eye to evidence of such exploitation.

"Mother" is the story of a woman who responds to an abused girl's silent cries of help. Nao (Yasuko Matsuyuki), an aloof 30-something woman who works reluctantly as an elementary school teacher, notices the unmistakable bruises on her first grade pupil Rena (Mana Ashida). Initially, like everyone else, Nao looks the other way.

But Rena's wretched desperation soon awakens a passion and determination in Nao. Together they skip town and embark on a risky journey pretending to be mother and child. "Mother" is the story of the transformation of a once disenchanted woman who suddenly takes on the role of a parent to a child who is starved for maternal love. The drama probes into the meaning of motherhood in modern society.

舞台是北海道。在室兰大学研究鸟类的铃原奈绪（松需泰子饰）是一个性格冷淡的35岁。因研究室的封锁只好到小学校当教师，但对教师职业一点热情也没有，只对鸟类感兴趣。与东京的家人也疏远，妹妹芽衣（酒井若菜饰 ）的婚礼也回了「缺席」。对这样的奈绪，母亲藤子（高畑淳子饰 ）非常担心，但是奈绪始终不愿接母亲的电话。

尽管奈绪不喜欢小孩，偶然的机会与一年级的怜南（芦田爱菜）聊了起来。怜南在周围人眼里是一个「奇怪的小孩」，却唯独对奈绪敞开心灵交谈。某一天奈绪看到怜南手腕上的紫斑和伤口，原来怜南经常被亲生母亲和其恋人饱受虐待。但怜南守口如瓶，学校也是暧昧的态度。最重要是奈绪犹豫不决对这种复杂的事情不愿理睬。

几天后，奈绪亲眼目睹怜南被虐待的情景，奈绪终于下定决心，叫出怜南，说到：“我要诱拐你。要成为你的妈妈。”