A story revolving around a dangerous drug ring and an undercover agent who works from the inside in an effort to take it down. A package containing methamphetamine shatters the once peaceful life of an average white collar worker named Dou Dou. The sender is Dou Dou's ex-boyfriend Jin Yuan who ran from their wedding seven years ago. Dou Dou changes course en route to the police station and decides to confrontJin Yuan. Detective Qiao Liang has been keeping tabs on Jin Yuan for his suspected involvement with the crime syndicate that range from drug trafficking to money laundering. Unwilling to let go of her ex, Dou Dou takes it upon herself to help Jin Yuan turn over a new leaf, oblivious to his real identity as an undercover cop.