We open with a shot of a flooded future London, and a narrator tells us that global warming has caused another world flood and London is submerged. After a little back story, we’re introduced to our badass anti-hero, Harley Stone. He jumps into his jeep and heads off towards a strip club in downtown London, trailed by detective Dick Durkin. After intimidating the guard dog and ordering some coffee, he’s approached by a woman who asks him to guard the bathroom door for her. While he’s outside, the killer he’s after strikes, shredding the woman’s heart from her chest. Harley hears her scream, and runs into the bathroom. He’s too late; the woman dead, the killer gone, and "I’m back" scrawled on the wall with the woman’s blood. He runs out looking for the killer, but there’s no sign. Harley leans down and talks to the dog, who he knows saw what happened.

Later that night, Durkin reports back to the chief, who gives Durkin the lowdown on Stone. He’s been transferred all over the world, suffers from massive survivor’s guilt after his partner, Foster, was killed by the same murderer, and that he lives on adrenaline, coffee, and chocolate. And he’s the best motherfuckin’ cop in the world. Stone, meanwhile, was incarcerated after the incident at the club, where it took four cops to wrestle him into submission. He’s released to go and see the chief. Stone runs into an old “friend” who gives him some shit, but Stone calmly stirs his coffee with the guy’s pen and moves on.

Stone goes into the chief’s office and tells him that the killer is back in town. Durkin reveals that he was following Stone, and the chief says he’s Stone’s new partner. Stone is not happy about this, but the argument is broken up by the arrival of a cooler with Stone’s name on it. Inside is a heart with a huge bit taken out of it. Stone and Durkin take off and head back to the strip club. Stone leaves Durkin in his car while he goes inside and lays in the bloody chalk outline of the body from the previous night. The owner comes in and threatens him with a shotgun, but Stone just talks to the dog again and ignores the man.

As Stone is leaving, he and Durkin are called to another murder scene. When they get there, they find a huge zodiac painted on the ceiling in blood. Durkin asks if the killer stood on the bed to paint it, and Stone replies that if so, he’ll be easy to find because he’d be over ten feet tall. He turns and sees a huge rat menacing Durkin from behind. The rat gets splattered all over the wall by Stone’s kickass hand cannon. Then Stone finds his partner’s old gun. At the same time, the mold of the tooth marks in the heart is brought to them. The teeth are huge fangs. Stone loses it and runs into the alley, blasting at shadows while the killer watches out of sight.

Durkin questions Stone about his sanity while Stone releases some tension on the ol’ PMS shooting range in the police station. After blowing the target to pieces with his cannon, he shows Durkin the mold of the tooth marks and tells him that the killer is some kind of monster. He leaves the station and goes to visit Foster’s grave, where he runs into his old flame, Michelle. They talk about Foster for a while, and they retire to Stone’s apartment, which kicks ass. There are pigeons flying all over, and a Harley-Davidson in the middle of the room.

While they’re sleeping, Stone has a nightmare about Foster’s disappearance. He wakes up with a pigeon perched on his head. After shooing the bird away, he goes down to the street where Durkin is sleeping in his jeep. He ties Durkin’s shoelaces together and sets off the car alarm. After the greatest dialogue about sex and jogging ever written, they go to a café for some breakfast. While they’re gone, the killer rips the trunk out of Durkin’s jeep and steals his shotgun.

Stone and Durkin have a discussion about Stone’s psychic link with the killer while the killer himself breaks into Stone’s apartment. They hoof it back to the building to find that the killer has made another attack. They have a gun battle with it, and it blows Durkin out the window with his own shotgun. It runs off and bites Michelle. After the paramedics show up and everyone is safe, Stone has another spaz attack and dreams of the killer raking its huge claws down his arm. When he wakes up, Durkin tells him that the claw scars are his link to the killer.

At the station, a DNA test comes in telling them that the killer has rat DNA, and DNA from all its victims, including Stone himself. Then they realize that the killer didn’t get the heart from the last victim, figure it will come back for the heart, and they run to the morgue. They encounter it again, and Durkin gets a look at it. He freaks out and starts ranting about needing bigger guns. Big big fucking guns! He starts downing coffee and chocolate candies, and pretty much turns into Stone. They take a little shopping trip to the armory, and come out with two rotary-cannon shotguns and a box full of mini-nuke grenades.

When they get back to Stone’s apartment, they find that the killer left a heart in his refrigerator. Michelle is in the bathtub scrubbing her hands in shock because she touched it. She reveals to Stone that Foster’s mother has killed herself. Durkin figures that her bite has promised her to the creature and she will be the next target. Stone sends him to the car while he comforts Michelle, and Durkin is attacked while Stone and Michelle make the sign of the triple-humped couch weasel. Stone runs to help Durkin, and Michelle is taken by the killer.

Durkin and Stone run back to the apartment, where Durkin sees a rat in Stone’s kitchen and blows the whole damn thing apart with one of the new guns. Then they find that the killer has clawed a map onto Durkin’s chest to lead them into its trap. They go to visit the Rat Catcher, who leads them into the sewer and gives them some keys to get them on their way. He promptly dies and is found in an elevator shaft a few minutes later. Durkin predicts that the killer not only thinks it’s Satan, but it actually IS Satan. Harley looks at him and utters the ultimate badass line, "Satan is in deep shit."

They hear Michelle scream and run to find her. She’s hanging by her hands in a circle of light, a magical protector, coming from an open manhole. Durkin frees her, but the creature attacks. Stone opens fire and drives it back into the water. He chases after it into an old subway car, where it sneaks up on him and pulls off his sunglasses and gun belt. I think it’s worth a mention that this thing has claws that put Freddy to shame. Durkin saves the day with one of the nuke grenades, and Stone shields Michelle from the explosion, kissing her through the blast. Smooth motherfucker. After the smoke clears, he runs in and fries the monster with a loose electric cable. It has no effect, and the slavering hell-beast grabs Stone by the throat, pinning him to the wall and preparing to open his chest. Stone beats the creature to the punch, though, and rips its heart out instead. He puts the barrel of his hand cannon to the squishy, screaming muscle and splatters it all over the walls. Stone and Michelle blow the body to pieces with the gatling guns. The trio rides into the sunrise with some kickass old Sinatra-style tune playing in the background while the water in the sewer starts to boil. We’re going to need some bigger fucking guns!

I don't think I really need to say again that this is my favorite movie. We'll just leave it at that. Go see it, or Nyarlathotep will turn your brain into scrambled eggs.