Sang, Prang and Tubtim (husband, wife and sister-in-law) jointly crew a barge that brings sand down the Chao Phaya river to Bangkok. Arriving in Bangkok, the dissatisfied wife, Prang, goes ashore seeking to improve her life. Sang sets out to find his wife who has been lost in the big city, a cabbie his only guide. Inevitably, Prang is eventually led to a young female 'casting agent', and is naively groomed for prostitution. Sang's search for her becomes a riveting tour of the seedy side of Westernised Bangkok.

The lyrical opening of this film as well as the story (a barge-man loses his wife as they arrive in a town) make comparison with Vigo's L'Atalante inevitable. Prince Chatri's film, however, is specific to Thailand - at once a Thai social conscience film of the kind Chatri pioneered in the 1970s, and an urban thriller-melodrama designed for mass appeal, but containing unexpected subtleties of emphasis. In Thailand the film bore the title The Sister-In-Law to play up the importance of the role of the wife's teenage sister who remains on the barge, effectively holding the family together through this psychological crisis, even while being one of its victims. Finally, there is the key figure of the taxi driver, whose alternately supportive/exploitative relationship with the desperate and naive husband Sang, within this bewildering modern metropolis, focuses keenly the way in which these river people are tourists even in their own city.