There's a legendary forest in Hong Kong that posses a disturbing and unique quality: It seems to be a hot spot for people who wants to commit suicide. Recent months have seen a surge in the number of deaths connected to this forrest, and the media has begun to take an interest. It is after all an intriguing and gruesome story. Up and coming reporter May has led the crusade to expose this place, aided somewhat unwillingly by her boyfriend, botanist Shum Shu-Hoi (Ekin Cheng), who has provided her with information about the forest.
Meanwhile CC Ha (Shu Qi), a driven police detective, has just taken on a new case involving a rape and murder in the forest. The previous detective on the case died of a heart attack right in the middle of a reconstruction at the original crime scene. CC suspects foul play and she decides to return to the forest to examine it more closly. To prevent her from getting lost in the vast forest she cleverly marks the trees she passes with numbers. However, when she attempts to find her way back later, the numbers appear to have been switched completely around. Something very strange is going on here.
Just before she descends into panic she stumbles upon a old man, the caretaker of the forest, who helps her back to civilization. He warns her about the forest and seems to know more than he's letting on.
Shum, still upset that his girlfriend used his help to indulge in a ludicrous supernatural story, continues his experiments with plants. He attempts to show that plants can be affected by music, but during his experiments he discovers something far more intriguing. Plants actually have feeling and perhaps they can even communicate with us.
Watching Shum explain his theories on TV CC decides to contact the botanist and procure his help with her investigation. Perhaps he can expose the secrets of the forest and help her crack the case.
Little do they know that no amount of science or clever theories can expose the mystery of the forest. It must be experienced first hand.