Yu Kwok-Kei cannot pay his debts and disguises himself as Ma Ka-Wai, his cousin Yu Lan-Fun's fiancee. He tries to kill Lan-Fun. A fisherman saves Fun. She believes that Ka-Wai was the attacker, but she can't understand why. After Fun has been missing, her family puts an announcement in the paper. Meanwhile, Chan Lan-Fong, who just comes to Hong Kong, looks like Fun and is brought to Yu's home. Fong's habits are totally different from Fun's, and she cannot recognise the family, who thinks Fun has amnesia. Fun knows that her family has mistaken somebody else for her, so she goes back home secretly and teaches Fong her habits and customs. Fong does what Fun tells her, and the family thinks that she has recovered. Kwok-Kei has a guilty conscience, so he disguises as Ka-Wai again, intending to kill Fun/Fong. But he fails and got arrested. Everybody learns that Kwok-Kei wanted to kill Fun. Moreover, Fun's mother discovers that Fong is Fun's lost twin sister and the family is reunited.
