In the year 2008, relentless rainfall has flooded vast parts of London, turning the city into a maze of submerged streets and shadowed corridors. A rookie officer, Dick Durkin, is paired with Harley Stone [Rutger Hauer], a battle-worn homicide detective who, as his commanding officer puts it, survives on “anxiety, coffee, and chocolate” after a wound that cost him his partner Foster three years earlier. With the murders resuming, Stone becomes hopelessly obsessed, and Durkin is ordered to stay glued to him at all times, documenting every sign of instability.
As they work the case, the pair comb through crime scenes that stubbornly resist ordinary explanation. The killer’s pattern seems tied to the lunar cycle, and shockingly, each victim has a part of an organ removed—apparently to be eaten. Laboratory tests at the crime scene reveal something even more disturbing: the killer’s blood contains multiple recombinant DNA strands, suggesting it has somehow absorbed the genetic material of its victims. The case grows stranger still with the personal complication of Michelle [Kim Cattrall], Foster’s wife, returning into Stone’s life after the years of secrets and an affair Stone once had with her.
Despite his rough exterior, Harley Stone begins to loosen under Durkin’s steady presence, and they start to form a bond. Durkin theorizes that the killer is taunting Stone directly, staging each brutal act at a location meant to lure him closer. Stone himself seems to share a psychic link with the monster, a connection born from the old wound that won him his nightmare reputation. The tension escalates when the killer targets a woman in Stone’s own apartment building, and then abducts Michelle, dragging the investigation toward a deeper, more personal abyss.
The chase leads them deep beneath the city into the flooded tunnels of the London Underground. They push forward to uncover the truth: the killer is not human but a large, terrifying creature that moves with terrifying speed and ferocity. Durkin uncovers a haunting memory—Stone had escaped the same creature a decade earlier, and it now fixates on killing him, using each appearance as a cruel lure. Armed and desperate, they trace the creature to its lair, an abandoned underground train station.
In a tense confrontation, they find Michelle suspended over the water as bait. Stone makes a decisive move to free her, triggering the monster’s arrival. A brutal fight ensues; Durkin manages to wound the creature’s chest, while Stone delivers the fatal blow, tearing out its heart. As they stagger out into the flooded corridors, bubbles rise to the surface—an ominous sign that the terror may not be finished, for there could be more than one creature lurking in the depths beneath London.
