Desirous Express (2000)

Yin is a lonely woman whose husband Keung treats her as his sex slave; she wants to kill him but never has the courage. He is always traveling to Shenzhen for whoring and once raped her friend Hong. Hong's partner Long has thrown her out of their apartment. One night after karaoke, Long and Yin begin a sexual affair. Long decides to kill Keung. Hong and Yin share their tragic past with Yin confessing about her fling with Long. Then Long turns up at Keung's apartment, having hatched a murderous plot with Yin...