A man is found dead inside an apartment with a strange noise, "Help. Help!" next to the body. Detective Frank Lam arrives at the scene with his commanding officer Yip Sir to find the sole survivor and eye witness. Yip Sir is convinced the deceased, Henry Tsui is killed by his partner in crime, Sunny Wong when they had a fight over how to divvy up the loot from an armed robbery a month ago. When Frank confronts Sunny, Sunny denies all allegations and names Yip Sir as the killer. Frank's only hope in cracking the case lies in the not-so-human witness left at the scene of the crime.