In the process of investigating a criminal case, Song Cheng, the criminal police captain who is persistent and has extraordinary powers of observation, discovered that the case was inextricably linked to another case four years ago.There is also a common witness Yu Xiao.

As Song Cheng deepened his investigation into the case, the secrets hidden in Yu Xiao's life were revealed one by one.With Song Cheng's encouragement and help, Yu Xiao joined forces with the police to find the truth.As the case progressed, the two men obtained more clues but also faced many obstacles.In the end, Song Cheng and Yu Xiao cooperated with each other to overcome obstacles and bring the real murderer to justice.