In the year 2008, heavy rainfall has flooded large areas of London. Rookie police officer Dick Durkin (Alastair Duncan) is assigned to partner wisecracking maverick Harley Stone (Rutger Hauer), a burnt-out and highly cynical homicide detective who was unable to prevent the murder of his partner by a serial killer several years previously. Now however, the murders have begun again and Stone and Durkin are assigned the case. After investigating the scenes of several killings, they appear no closer to identifying the killer, with their only clues being that the murders seem to be linked to the lunar cycle, and that the killer has multiple DNA strands, having absorbed the DNA of the victims. Finally, after Stone's girlfriend Michelle (Kim Cattrall) is kidnapped, the detectives track the killer deep into the flooded and disused London Underground system and discover the truth: the killer is not human. It's a horrific and possibly demonic form of life that is fast, savage, bloodthirsty and fixated upon killing Stone just as it previously killed his partner. As each killing and appearance of the monster is an attempt to lure them closer and closer, can Stone and Durkin rescue Michelle and save London and themselves from true evil?