做事执着、具有超凡观察力的刑警队长宋诚在调查一起刑事案件的过程中，发现该案和四年前另一起案件有着千丝万缕的关联，而与这两起案件卷入到一起的还有一个共同的证人俞笑。随着宋诚对案件调查的深入，隐藏在俞笑生活中的秘密被逐一揭开。在宋诚的鼓励和帮助下，俞笑与警方联手共同寻找真相。随着案件的深入，二人在得到更多线索的同时，也面临诸多阻力。最终，宋诚和俞笑互相配合，克服阻碍，将真凶绳之以法。

Detective Song Cheng discovers a link between a current case and an unsolved crime from four years ago, both tied to key witness Yu Xiao. As he digs deeper, Yu Xiao’s hidden past comes to light. She joins the investigation with Song Cheng’s support, but mounting obstacles threaten their pursuit of the truth. Together, they fight to uncover the real culprit and bring justice to light.