Interpol officer Xu Guo Ying resigns after she failed to protect a suspect. Following advice from her superior, she continues witness-hunting for international cases. Korean idol Kwon Seung-hyun is suspected for murder of Park Kyo-eun. Korean police searches for a Singaporean girl, Hannah, who was with the victim that night. While looking for Hannah, Guo Ying meets Yu Xuan and Zhi Ming.

Hannah, who was kidnapped, manages to escape. She then changes her statement to say that Kwon Seung-hyun had killed Park Kyo-eun, and agrees to testify in Korea. Guo Ying senses something is amiss. She later finds out that Hannah's sister was taken hostage, and she had been forced to give a false testimony. Guo Ying, Yu Xuan and Zhi Ming set off to rescue Hannah's sister but is surrounded...

Guo Ying and company rescue Hannah's sister. Hannah reveals that Kwon Seung-hyun's business partner Gong Jung-hoon is the real murderer and police arrests him. Yu Xuan's aunt Mei Ru agrees to help her online lover transfer a parcel. Turns out the parcel contains drugs, and she is arrested for suspected drug dealing. Yu Xuan seeks Guo Ying's help in tracking down the drug trafficking organisation.

While investigating a case, Ying Jie finds the passport of Yu Wen Guang, who should have been dead for years. Yu Wen Guang was the informant of Ying Jie's mother, Tang Mei Xiu. She was killed while having a rendezvous with him for a drug-dealing case. Guo Ying, Yu Xuan and Zhi Ming investigates the bungalow where his bones were discovered, and finds another set of bones!

Guo Ying asks for the drug investigation documents, but Ying Jie makes an excuse to refuse. Guo Ying realises that Yao Kang was the one who hindered her from getting the documents and confronts him. Yao Kang says he does not want Ying Jie to take the risk, but eventually gives in and hands her the papers. The documents turns out to be fake, causing Guo Ying's investigation to bear no result.

Yu Xuan leads Guo Ying to meet Li Na, and the two trail her secretly. Li Na discovers them but is unable to shake them off her trail. Guo Ying gets hold of her and asks her where Wen Guang is. Li Na pretends to be shocked and seeks help, causing a crowd to form. A car appears and drives off with Li Na. Guo Ying, unable to stop the vehicle, discovers the driver is Wen Guang!

Guo Ying finds Li Na on the yacht and asks her where Wen Guang is. Li Na says she does not know and lies about how Wen Guang had killed someone for her. Guo Ying's guard is let down, and Li Na takes the opportunity to poison her and escape. As the poison starts to take effect, Zhi Ming does his best to escort Guo Ying back on land for treatment despite being poisoned himself.

Guo Ying receives tip off about important evidence for an arms smuggling case. Finding it suspicious, she reports to Wu Sir, who deploys Ying Jie and a few other CID personnel to investigate. In the house, Ying Jie finds a microchip and hides it. As Ying Jie was going to check the microchip data, Guo Ying appears. She realises her father, Yao Kang, is the mole in the police force.

Having failed to protect the witness in an international drug smuggling case, Interpol Officer Xu Guo Ying resigned as a result. In a twist of fate, Guo Ying took on witness-hunting, where in the process, Funeral planner Wang Yuxuan and arcade staff Chen Zhi Ming joined her league of justice. But Guo Ying soon realized Zhi Ming and Yuxuan were not what they appeared to be.

Mary wants Zhi Ming to invite Guo Ying and Yu Xuan home for a meal. Yu Xuan uses this opportunity to ask Zhi Ming about his background and learns that he was a homeless orphan until Mary adopted him. Although Zhi Ming lost his memory, he remembers that he was kidnapped. Yu Xuan is astonished as she recalls a boy she had frequently played with getting kidnapped when she was a child.

Guo Ying asks Dex about the tattoo, and he passes her a Thai tattoo master's name card. Yu Xuan is puzzled about his motive, as she knows the tattoo master has already passed away. She finds out from Johnny that Myanmar army rebels had killed Dex's parents when he was young, and he has been keeping a lookout for them, not ruling out that Dex could have killed these people.

Guo Ying tells Yu Xuan and Zhi Ming that the three victims were rebels who massacred a Myanmar village 23 years ago. They let Nick investigate the massacre's survivors, not ruling out that the survivors took their revenge. Yu Xuan suspects Dex is the murderer and reminds Dex to be careful in their conversation and that she is willing to help. Dex does not comment on it and changes the topic.

Dex and Da Peng bring Dan Nong to the freezer warehouse, where they interrogate him to reveal the mastermind behind the village massacre. Dan Nong refuses to speak. Guo Ying and her two partners track them down, and Dex urges Da Peng to leave, but Da Peng holds Dan Nong hostage and forces Guo Ying to retreat. Meanwhile, the police arrive. Upon seeing there's no way out, Da Peng kills Dan Nong. Dex和同乡大鹏将丹农带到冷藏库，逼问他到底是谁指使他们走私军火，并屠杀村民，丹农不愿透露...

The Hong Kong police want Nick, who used to be an undercover agent, to testify in court for a gang vendetta case. However, the gang kidnaps him, ties him up and dumps him into the sea. As Nick was on the brink of death, Guo Ying and her two partners arrive in time, and Zhi Ming plunges into the waters to rescue him. Nick曾在香港当过卧底，香港警方要Nick回去为一起黑帮仇杀案出庭作证，黑帮派人将Nick掳走，在他身上绑上铅块，将他沉入海里。Nick性命垂危之际，幸好帼瑛等人来到，志明跳入水中将Nick救起。

Li Na claims to hold information on Guo Ying's mother's death. Guo Ying follows her, but Li Na takes the chance to escape. While Guo Ying is left feeling vexed, she meets Yao Kang. Yao Kang instructs the police to investigate Li Na's whereabouts and tells Guo Ying to stop interfering. Yao Kang becomes nervous when he hears Guo Ying tell him Li Na has information about her mum's murderer. 莉娜声称手上有帼瑛母亲死亡真相的资料，帼瑛随她去拿资料，莉娜乘机逃走。帼瑛懊恼之际，遇见耀康...

Guo Ying finds a hidden package at Li Na's old house, and she finds Yao Kang's ring inside! Guo Ying has a hunch that her mother's death is related to her father. She goes home to ask Yao Kang, and he tries to explain. Ying Jie guesses their mum knew their father had betrayed the police and urges him to turn himself in, leading to his intention to kill. This revelation shocks Guo Ying. 帼瑛在莉娜旧居找到莉娜藏在那里的一包东西，里头竟有耀康的戒指！帼瑛隐隐觉得母亲的死和父亲有关，回家责问耀康，耀康试图辩解。

In her grief, Guo Ying kills Antonio in a car accident. At her wit's end, she calls Yao Kang for help. He disposes of the corpse and teaches Guo Ying how to respond to the police. In a daze, she follows Yao Kang's plan. Ying Jie asks about the car accident after they return home. Yao Kang explains for Guo Ying, but Ying Jie is full of doubts and senses that Guo Ying is hiding something. 帼瑛悲愤下撞死Antonio，不知如何是好，向耀康求助。耀康赶来帮忙处理尸体，并教帼瑛如何应对警察。帼瑛六神无主...

Mary knows Zhi Ming doesn't wish to go back to base because of Yu Xuan. She decides to hire an assassin to get rid of Dex and Yu Xuan. Dex and Yu Xuan both receive a text from Aaron to meet at the yacht club. When they reached, they realised it was a trap all along. The assassin hunts them down, and Dex sacrifices himself for Yu Xuan. Before he died, Dex confesses his love to Yu Xuan. Mary知道志明不想回基地是因为雨萱，决定派杀手去解决Dex和雨萱。Dex和雨萱分别接到Aaron的简讯...

Zhi Ming was about to search for the homeless man when Guo Ying finds him. Guo Ying accompanies him, and the two find the homeless man. They finally claim the necklace pendant from him, but Guo Ying suddenly attacks Zhi Ming and snatches it away. Although Zhi Ming had the chance to get the pendant back, he did not want to hurt Guo Ying. Guo Ying takes the chance and escapes with the pendant. 帼瑛去找志明，志明正要去找流浪汉，帼瑛愿陪他一起去。两人辗转找到流浪汉，终于从他手中拿到项链坠子...

Guo Ying is kidnapped, Zhi Ming and Yu Xuan also fall prey to assassins. When Zhi Ming wakes up, he realises Guo Ying and Yu Xuan are tied up, and Mary has a ticking time bomb attached to her. Mary tells him Lao Ying is angry because Zhi Ming refuses to obey to him. Zhi Ming is asked to choose between killing Guo Ying and Yu Xuan, or have the time bomb on Mary explode. What will Zhi Ming do? 帼瑛突然被人掳走，志明和雨萱也遭到杀手袭击。志明不醒人事，醒来后发现帼瑛和雨萱被绑在一起...