After a long investigation, which includes a few dangerous confrontations with a "suspect", Yau discovers Lau's secret and dark past. Chow Yuen-sing had murdered Lau's family members in Macau several years ago when Lau was still a boy, and he bribed the police to close the case. Lau survived, took on a new identity, and grew up in an orphanage before moving to Hong Kong, where he became a police officer. Lau seeks vengeance on Chow and he pretended to fall in love with Susan and married her. He attempts to kill Susan by drugging her and locking her inside the kitchen after turning on the gas. Susan survives, but is badly injured because there was an explosion, and ends up in hospital.