Unforgivable

Yifan joins SOD successfully. His first case is a serial killing where the perpetrator has the habit of stealing the victim’s shoelace as his trophy. This modus operandi leads SOD to believe that it is connected to a sexual crime committed 10 years ago. As they try to search for clues from both cases, the perp kills again. This time, he did not wait for 10 years.

Shu Ya discovers the serial killer is using his pet dog to lure the victims, after which he assaults them. They find a suspect following this clue. However the suspect is exceptionally cunning, denying it all. Shu Ya engages in a battle of wit against him.

Shu Ya entrusts a marital rape and domestic violence case into Guan Lin’s hands, hoping she can handle it professionally. Unfortunately, Guan Lin brings her personal feeling into the case yet again, failing to be objective. Tension rises as their belief system clashes.

A maid goes to the hospital seeking medical attention. The doctor suspects she was sexually assaulted and reports it to the police. However, she leaves the hospital before the police gets there. SOD tries to seek her out and discovers that she is taking care of a dementia old man, raising confusion on who is the real vulnerable party?

Guan Lin initiates an investigation about an elderly person being molested. Jun hao and Yifan offer their help, deepening the bond among these three. Meanwhile, SOD identifies the maid’s attacker, but the suspect schemes to persuade the maid to change her testimony. Junhao accidentally discovers that Guan Lin is using police resources to search for her birth mother.

A man is being castrated outside a bar. The team reckons this could be a hate crime or act of vengeance. As they follow the leads, they discover that the victim used to be a teacher and has a criminal record. Meanwhile, Junhao promises to help Guan Lin keep her secret.

Guan Lin visits the victim at the hospital and witnesses someone attacking him. The person admits to being the one who castrated the victim, painfully revealing the reason behind it. Suspecting that the victim has not changed his criminal ways, SOD decide to investigate him and bring him to justice.

A teenager discovers that he is attracted to children. He tries to be honest with his parents but fails to receive any help from them. The team arrests an old pimp Gao Guang Sheng, unaware that he is Shu Ya's biological father. As the teenager grows older, it is revealed that he is Kuan Weiliang. His parents’ contempt pushes Weiliang to embrace his pedophilia instead, embarking on a path of crime.

55’s daughter Shanshan starts to take nude photo and watch pornography under the influence of her online boyfriend. Police psychologist Jackie steps in to help find out whether she is being catfished. At the same time, Shu Ya suspects those actors in the pornography could be underage and decides to investigate. Junhao collapses and is hospitalized, Guan Lin takes care of him, bringing them closer.

SOD discovers that the pornography is being released by a channel called SG Satay. To attract more subscribers, the suspect starts to install pinhole cameras in the women's restroom. While investigating the case, Jun hao's grandmother passes away. The team tries to be his source of support and comfort. Although Yifan has feelings for Guan Lin, he cannot help but notice her affection for Junhao.

After being released from the jail, Chen Yong Ren holds an entire eatery hostage with a gas cylinder. He demands the police to clear him of his attempted rape and murder charges from over 20 years ago. SOD is roped in to investigate. The team re-interview all individuals involved in that case. Meanwhile, police at the hostage scene brings in Yong Ren's daughter to help.

Time is ticking away, the team decides to set a trap to expose the individual involved in Yong Ren's case. Seeing how his daughter is filled with disdain towards his actions, Yong Ren loses all hopes and attempts to ignite the gas cylinder. Guan Lin confesses her feelings to Junhao.

Upon interrogation, a suspect confesses to killing the victim in the hotel murder case. However, the described crime process does not match the victim's actual cause of death. The team remains in doubt. Meanwhile, due to trouble created by the victim, Gao Guang Sheng is being hunted down by the people controlling the prostitution ring.

With Shu Ya's help, Guan Lin finally locates her mother, Wang Jinxiang. She is reluctant to acknowledge her daughter due to years of shame and fear, but eventually gives in after seeing how much Guan Lin misses her. Weiliang kidnaps Qiqi, a little girl that Jinxiang treasures dearly. Qiqi desperately seeks help, hoping to escape from Weiliang's clutches.

A member of SOD suddenly disappears. As the search begins, tragic news comes unexpectedly. The entire team is plunged into a state of sorrow and confusion. Detective Wang from the major crime unit is assigned to investigate this case. Weiliang's actions of kidnapping children are exposed. Feeling the pressure, his behaviour becomes increasingly irrational and dangerous.

Two little girls go missing at around the same time. SOD and Detective Wang's team must collaborate to solve the case. Time is of the essence as they fear for the girls' safety. Weiliang's wife and family begin to suspect him. The parents of one of the missing girls are famous influencers, they publicly criticize the police, resulting in SOD being removed from the investigation.

The members of SOD decide to defy orders and conduct their own private investigation. They discover that the series of cases are all connected to Weiliang. Meanwhile, Weiliang's wife can no longer conceal her suspicions and confronts him directly. Weiliang realizes that the police are onto him and goes on the run. The police launch a massive pursuit.