A very straightforward genre film from Yau. The pivot from horror to drama and mystery is a staple of the Asian horror niche, Yau is simply playing it by the numbers here. As long as you don't expect the world from this film, and you don't crave originality, Nightmare has plenty to offer, certainly for greedy and insatiable genre fans.
Hao Dong suffers from sleep deprivation. While he's awake one night, he sees a woman living across the street being murdered in her apartment. When Dong goes to check on her, he finds an empty place and no sign of a corpse. His girlfriend tells him it's just a hallucination, but when it happens again Dong begins to suspect it's an old trauma rearing it's head.
Nightmare is built on mood. It's certainly not the scariest film you've ever seen, not the most surprising or memorable one either. But Yau's direction does feel very accomplished. The cinematography is polished, the soundtrack moody and the performances are on point. Very solid genre material in other words. I had plenty of fun with this one.