一家位於琵琶湖畔的護理之家，驚傳百歲老翁離奇命案。負責調查的俊秀刑警和難脫嫌疑的冷豔照護人員，在審訊期間暗通款曲，私下沉迷於激情禁忌遊戲。他卸下正義化身發號施令，她拋棄天使形象悉聽遵便。肉體的交涉越發淫猥，褪去羞恥的狂想日漸膨脹。隨著案情陷入膠著，墮入黑暗深淵的男女，與此案相關人的傷痛記憶，跨越時空激起漣漪，悄悄從深邃的湖中浮現。波光如鏡，天地絕美無邊，人性之惡卻也俯拾即是。

A 100-year-old resident of a Lake Biwa nursing home dies mysteriously. Did a respirator keeping him alive suddenly malfunction, or was he murdered? A young detective on the case meets a female caregiver. The investigation runs into a dead end, but the two fall into a passionate but forbidden relationship. Terrifying memories emerge from the vast, deep lake to ensnare the detectives on the case, the caregivers, and a reporter trying to uncover a hidden past.