Conspiracy (2000)

Maggie[Bessie Chan] is having a bit of a relationship crisis after her boyfriend Andy[Micheal Tse] returns to Hong Kong from a trip to Thailand. She spied Andy with new girl Sharon[Sophie Ngan] at the airport and he seems to have lost all sexual interest in her. Maggie's old habit of sleepwalking returns after ten years, just as Chiang - Andy's boss - is murdered. When she wakes up on another night with a kitchen knife in her hands, she begins to worry that she could be involved in some way. And then the sister of Sharon is also murdered