After a mission failed, Chen Yan, the ace of the Security Bureau, was deprived of promotion qualifications and demoted to a clerk in the archives room. He originally thought he would be silent, but when he was sorting out old files, he found a incomplete list - it recorded the true identity of the previous candidates for 'Long Yuan', and his name was crossed out and replaced by the new codename 'Long Yuan'. An identity that does not belong to him has become his only bargaining chip to return to the front line. He faked his name and returned to the operation under the name of "Long Yuan", but found that he stepped on the tip of the conspiracy every step of the way: the mission mistake that year was the plot of the insider White Crow, and the candidates on the list were being eliminated one by one. The only colleague who trusted him, Shen Que, was actually a pawn planted by the insider. Chen Yan must find out the truth behind the list before his identity is exposed, and at the same time protect Shen Que from being silenced by Bai Ya. He has retired old Zhou secretly guiding him, intelligence dealer A Lan to provide clues, and technician Uncle Tie to modify equipment for him, but every step comes with a price - every time he uses the identity of 'Long Yuan', he is one step closer to the truth and one step closer to death. When the last page of the list was revealed, Chen Yan discovered that the true meaning of 'Long Yuan' was not a code name, but a taboo that must be erased. Can he find a way between his identity and the truth? Or is he destined to be the last name crossed off the list?
