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.

But, perhaps, there was another motive for the forensic artist to approach the young officer...

A chance encounter separates Xie Lanshan from Shen Liufei. Though physically apart, a mysterious letter to the police department entangles them in the same case involving a years old murder and a current hostage situation. Seeking a way out of the dire situation, their hearts become inexplicably drawn toward each other.

Meanwhile, Xie Lanshan's former teammates arrive to investigate the sudden proliferation of drugs in the city. Although they used to fight alongside one another, not everyone is convinced of their unsung hero's loyalty. Adding to the stakes is Song Qilian. Unable to let go of the man from her past, she conducts her own investigation into Xie Lanshan's identity.

Hidden memories grow ever clearer, and Xie Lanshan comes ever closer to answering his question, "Who am I?"

Though, everyone else may already know the answer…