Following the mysterious death of his colleague, CIB Chief Inspector Michael Miu discovers that the five undercover cops under his colleague's watch have gone missing. As the undercovers hold highly confidential information concerning the police force and society's safety, Michael is determined to find them. He finally tracks down one of the missing agents - Charmaine Sheh, posing as the owner of a foot massage shop. In order to recover her identity, Charmaine agrees to infiltrate the triads. She manages to get close to Raymond Lam, a member of an illegal gambling group. The two begin an elusive relationship built on lies. But just as Charmaine edges closer to the truth, Michael suddenly halts the operation. This is when Sharon Chan from the ICAC intervenes into the case. Through Sharon, Michael meets her elder sister, Elena Kong. Meanwhile, the triad leader Benz Hui has been released from jail and his assistant Sammy Sum's actions is catching Michael's attention. The relationships between the police and the triad become increasingly complex; with everyone claiming to be fighting for justice, who truly dictates justice?