Choi Fong (Jessica Hsuan) is the eldest daughter of the Ling family that includes her oft-absent father, stepmother and stepsister Choi Dip (Leila Tong). Like Cinderella, she undertakes all the housework, does the grocery shopping, cooks for the family, and prevents her father's antique collection from falling prey to her stepmother's gambling appetite.
One day, Mrs. Ling's vice finally catches up with her and to pay a particular debt, Choi Dip is consigned to marry the village idiot Ding Seung Wong or Ah Wong (Roger Kwok), who is about as intelligent as an eight-year old. Unwilling to commit her real daughter to a life of misery, Mrs. Ling arranges a double wedding and switches the brides so that Choi Fong ends up marrying Ah Wong, while Choi Dip marries Bao Gai Zong (Raymond Cho), the scion of the wealthy Bao family. And so begins Choi Fong's merry schemes to escape from her marriage with Ah Wong who, to her consternation, takes an immediate liking to her and clings to herlike sticky biscuit dough.
After several failed attempts evading her fate, Choi Fong gradually resigns herself to play Ah Wong's "lou por jai" or "little wife". One day, a strange girl Yeung Pui Kwan (Winnie Yeung) arrives in town and claims Ah Wong for her fiancé. Choi Fong soon learns that Ah Wong was actually a bright young man and the real heir of the Bao family who inexplicably disappeared two years ago, only to reappear with an IQ of an eight-year old.
Hoping to return Ah Wong to his rightful babysitter as soon as possible, Choi Fong agrees to help Pui Kwan get to the root of the mystery. So the girls embark on a campaign to expose the bogus Bao Gai Zong, reinstate Ah Wong as the rightful heir, and help him regain his memory. But just as Ah Wong begins to show signs of recovery, Choi Fong realises to her dismay that she has fallen for him...