Old Mr. Lo has three sons and the youngest one Lo Kung is his favorite. However, Kung does nothing but fool around all day long. Old Mr. Lo is very annoyed about this. The relationship between father and son is thus affected. So on Kung's birthday, his two brothers decide to play a joke on him. They trick him into believing he has won the lottery. Kung is so happy that he spends a tremendous amount of money. When he realizes he is in huge debt, he pretends to go insane and the whole family believes him.

Kate stars opposite Richie Ren (or Jen, depending on what rocks your boat), as couple Rachel and Fat. They're the atypical modern day couple living it up in Beijing, though the latter is suspect of the former's promiscuity. He loathes the time when he has to bring his girlfriend back to the village to meet his parents, and to get the stamp of approval from his father (played by Yuen Wah). So they device a plan, and that is to look for a substitute girlfriend (hence the title Contract Lover), whose mission is to be as disgusting as possible, so that Dad will tell Fat to find anyone else better than the current beau, and hence, for Fat to introduce Rachel.