A murder case involving a child victim occurs near the Han River. Jin-Soo, a detective whose life has been in shambles since his own daughter was kidnapped and killed, is assigned to this case. Obsessed with child-related cases since his own tragedy, Jin-Soo becomes deeply engrossed in the investigation. One day, Jin-Soo is approached by his high school classmate, a famous actress, who asks him to find her missing sister. As he investigates, he discovers disturbing connections between her and the child found by the Han River. Unsettling truths gradually begin to unravel.

아이를 유괴로 잃은 뒤 아동사건에 과도한 집착을 보이며 경찰 내 문제적 인물로 낙인찍힌 이진수가 한강변 아동 사체사건을 처리하던 중 자신을 찾아온 고교동창 도미애의 부탁으로 그의 동생 도미옥을 찾게 되며 일어나는 일을 그린 이야기.