Lin Mo transmigrates into the body of Lin Jianjun's son. His father, a police detective, has just died in the line of duty. At his father's funeral, the police badge number "89757" left behind by his father grows strangely hot, and unfamiliar memories flood into him. Taking his father's place, he joins the municipal Public Security Bureau's archives department. Late one night, he comes across an encrypted file marked "990415." His badge number resonates with it, prompting him to investigate his father's "accidental" death.
In the archives, he finds his father's notes mentioning "the docks," "a mole," and "the Cleaner." He also gets assigned to fieldwork with the criminal investigation team, where he is attacked by a masked assailant and obtains an encrypted chip, pinpointing the Cleaner organization's trail. As the team gradually comes together, Lin Mo uses his "blood-red intuition" to crack a string of cases, including poisoning at a pet shop and body parts hidden in a package. He discovers that the cases all lead back to the "990415 murder of wealthy businessman Zhao Tiancheng" ten years ago.
As the investigation deepens, Lin Mo activates the Criminal Investigation Heroic Spirit System, unlocking fragments of heroic spirits such as forensic pathologist Lin Jing and gaining skills like "deciphering the language of corpses." He exposes Old Zhou from the archives department as his father's informant and discovers that Zhang Tao, a mole in the police force known as "Eagle," colluded with the Cleaner. His father had actually been undercover and was silenced after discovering the mole. In the end, Lin Mo and his teammates arrest Zhang Tao, solve the 990415 case, and confirm that his father was undercover. But the shadow of the "Shadow Organization" has begun to emerge, and the secret behind badge number "89757" remains unsolved.
