After 27 weeks of training in the police academy, Wen Li, Bai Qiao and other policemen finally passed the test. Two new brake brothers were sent to the same squad in Yau Ma Tei Division and became real policemen. Bai Qiao hopes to become an inspector as soon as possible to repay his dead father and take good care of his grandfather. In order to be promoted as soon as possible, Bai Qiao strictly abides by the general rules of the police and does everything by the book, seeking no merit but no fault. Wen Li's personality is more impulsive than Bai Qiao's, and his definition of a good policeman is different, so his way of doing things is different.

During a patrol, Baiqiao stopped a group of bewitched children. Because of his inexperience, he was teased by Jing Feng, the leader of the bewitch, and later complained by Jing Feng's men, which made Bai Qiaoqiao under the internal investigation of the police. Bai Qiao is very worried about this, fearing that the incident will be recorded, which will affect the promotion prospects.

After a night shift, Ailin and Li Wen happened to meet Jingfeng, silly strong and others. Feeling suspicious, they followed Jingfeng and others with Li Wen, hoping to find evidence of Jingfeng silly strong. When Baiqiao was on duty, he found that the two men were moving, but it was too late for Li Wen to go. He could only see Ailin lying on the ground and being shot and killed by silly strong.

Seeing that Irene was shot, Bai Qiao was greatly shocked, and at that time he was confused and unacceptable about what had happened. Bai Qiao couldn't bear to break with Wen Li and thought that Wen Li should take full responsibility for Irene's death. Because Bai Qiao felt that Wen Li wanted to solve the case, she would take Irene to track down Feng Jing and others, and there was a bad feeling between them.

Six months later, Wen Li and Bai Qiao are still uniformed police officers in Yau Ma Tei Division. Only then did they know that Jing Feng, whom Bai Qiao met six months ago, was undercover. Now he has made a great contribution, and was promoted to Shazhan, and transferred to the uniform patrol of two people to become their boss.

Usually, the police must serve as patrol officers in the uniform team for more than one year before they can be selected as the "police mobile unit" in the mobile unit for training. But after half a year, Bai Qiao recommended himself to his boss to join the camp, because joining the mobile force is a necessary condition for the promotion of police officers. Jingfeng needs to join the Mobile Army for new training because of his new promotion to Shazhan.

Three people need to face a rigorous training period of 12 weeks. Wen Li and Bai Qiao fought in the squad for the best police officer in the mobile unit. The most important thing for mobile troops is team spirit. The infighting between Wen Li and Bai Qiao greatly affected the team's performance, which made Feng Jing very headache. Jing Feng couldn't bear to see the two brothers make the same mistake as sir Li. In order to make them reconciled, Jing Feng told Baiqiao that it was not the impulse to write that killed Aileen that day.

Later, the mobile army took part in a WTO action. The demonstration not only broke through the defense line of the mobile army, but also made the good friends who had turned against each other understand how precious their friendship was. Finally, this WTO entry action not only made the two men reconciled as before, but also made them become better brothers with more tacit understanding and closer relationship.

Just as the three men became a closely coordinated mobile detachment, Bai Qiao began to see the scene of Eileen's death. The psychological consultant reminded Bai Qiao Ailin of the truth of her death that day, but Bai Qiao didn't know how to face it.