On a rainy night, ancient book restorer Chen Shenzhi died in a locked study room, and the only copy that had been handed down from ancient times disappeared. The calm and keen female police detective Lin Yan was ordered to investigate the case with her partner Su Xiao, who is good at criminal psychological profiling. The fishing line in the secret room and the gypsum powder on the inkstone, every clue hides a murderous intention; the disappearance case twenty years ago and the secret behind the mysterious password make the two people step by step into a serial conspiracy. They are comrades-in-arms who have a perfect understanding when solving crimes, and they also rely on each other to protect each other in dangerous situations. On the way to pursue the murderer, the truth and emotions grow together. When the mastermind behind the scenes shows his fangs, can they work together to win this puzzle game where their lives are the bet?
Intention: truth and redemption, walking together in darkness.