Lu Jinchuan is a calm and meticulous criminal investigation captain, and Xie Zhaohui is a former forensic doctor who suffered a mental breakdown due to the destruction of evidence. When a serial murder case reappeared the fingerprints of the old case, Lu Jinchuan found Xie Zhaohui standing in front of the ashes smiling on the night he burned the key evidence - she went crazy that night, and he ignited the truth with his own hands. The two confront each other in the gap between memory and sin. One tries to cover it up, the other insists on uncovering it, and every piece of burned paper is engraved with the past they buried together.
