An unforgivable crime that stares directly into the darkness of the human heart.

To address rising sex crimes, the police form the Sexual Offence Department (SOD) led by Gao Shuya, a compassionate leader with a troubled past. Her team, including a consultant who saved her as a child, works on cases of serial sexual homicide, pornography, and old rape cases. As public pressure mounts, the team struggles against the trauma surrounding both victims and perpetrators. Their toughest challenge is a serial rapist dubbed "Werewolf," threatening their mission and the team's future.