In the Dark: Volume 1 (In the Dark, 1)

Even if trapped in darkness, one will always search for the light.
This is a story of a young police officer searching for the answer to "Who am I?"
In the past, Xie Lanshan was an undercover drug enforcement officer who infiltrated the Golden Triangle's most feared armed organization as drug lord Mu Kun's right-hand man. After successfully returning to his post from the operation, an accidental case of police misconduct triggers a series of unexplainable headaches and hidden memories that begin to haunt him.
While investigating the truth behind his father's death of many years ago, Xie Lanshan utilizes his unique and sharp thinking from the perspective of a psychotic murderer to solve difficult cases around him. Plagued by this growing change and instability of both his mental health and personality, he meets a mysterious forensic sketch artist named Shen Liufei. Together, the two men will maintain a strange relationship; as friends and enemies, they solve mysterious cases one by one.