The film tells the story of Xu Rulin, a prosecutor who practices extreme justice, and his apprentice Luo Xun, who becomes a criminal defense lawyer, who reunites in court. The former master and apprentice have become rivals, knowing each other well and confronting each other to the extreme. In many cases, the two confront each other, digging into the meaning of the law, exhausting the reasoning, untying the "legal knot" with a court defense full of twists and turns, and untying the "heart knot" with a soothing warmth.