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…
