SECRET UPON SECRET...CRIME UPON CRIMEAs Sergeant Luo Wenzhou and his team investigate treachery and hunt for a traitor at Yancheng Municipal Public Security Bureau, they delve deep into the institution 's past. They quickly uncover further betrayals...and hints about the shadowy force that 's seemingly haunted each of their recent major cases.The initial Sketchpad Project, which once appeared benign, is now starting to seem like a more sinister undertaking. So when the project was revived, why was Fei Du eager to take a role? And why has his own mind blocked out crucial details of his past?The team 's findings lead Tao Ran to an isolated county to question a nondescript local. But the man Tao Ran tracks down has a more disturbing secret than they guessed, and Tao Ran 's attempts to uncover it provoke that shadowy force again.