Long-time friends and small-time criminals Eddy, Tom, Soap, and Bacon put together £100,000 so that Eddy, a genius card sharp, can buy into one of “Hatchet” Harry Lonsdale’s high-stakes three-card brag games. The game is rigged, however, and the friends end up massively indebted to Harry for £500,000. Harry then sends his debt collector Big Chris, who is often accompanied by his son, Little Chris, to ensure that the debt is paid within a week.
Harry is also interested in a pair of expensive antique shotguns that are up for auction and gets his enforcer Barry “the Baptist” to hire a couple of thieves, Gary and Dean, to steal them from a bankrupt lord. The two turn out to be highly incompetent and unwittingly sell the shotguns to Nick “the Greek”, a local fence. After learning this, an enraged Barry threatens the two into getting the guns back. Eddy returns home one day and overhears his neighbours — a gang of robbers led by a brutal man called “Dog” — planning a heist on some cannabis growers loaded with cash and drugs. Eddy relays this information to the group, intending for them to rob the neighbours as they come back from their heist. In preparation for the robbery, Tom visits Nick the Greek to buy weapons, and ends up buying the two antique shotguns.
The neighbours’ heist gets underway, and despite a gang member being killed by his own Bren gun, and an incriminating encounter with a traffic warden, the job is a success; they return home with a duffel bag filled with money and a van loaded with bags of marijuana. Eddy and his friends ambush them as planned, and later return to stash their loot next door. They then have Nick fence the drugs to Rory Breaker, a gangster with a reputation for violence. Rory agrees to the deal but later learns that the drugs were stolen from his own growers. Rory threatens Nick into giving him Eddy’s address and brings along one of the growers, Winston, to identify the robbers.
Eddy and his friends spend the night at Eddy’s father’s bar to celebrate. Meanwhile, Dog’s crew accidentally learns that their neighbours are the ones who robbed them, and set up an ambush in Eddy’s flat. Rory and his gang arrive instead and a shootout ensues, resulting in the deaths of all but Dog and Winston. Winston leaves with the drugs; Dog leaves with the two shotguns and the money but is waylaid by Big Chris, who knocks him out and takes everything. Gary and Dean, having learned who bought the shotguns and not knowing that Chris works for Harry, follows Chris to Harry’s place. Chris delivers the money and guns to Harry, but when he returns to his car he finds Dog holding Little Chris at knifepoint, demanding the money be returned to him. Chris complies and starts the car. Meanwhile, Gary and Dean burst into Harry’s office, starting a confrontation that ends up killing them both, and Harry and Barry as well.
Returning to see the carnage at their flat and their loot missing, Eddy and his friends head to Harry’s, but when they discover Harry’s corpse they decide to take the money for themselves. Before they are able to leave, Chris crashes into their car to disable Dog, and then brutally bludgeons him to death with his car door. He then takes the debt money back from the unconscious friends, but allows Tom to leave with the antique shotguns after a brief standoff in Harry’s office.
The friends are arrested but declared innocent of recent events after the traffic warden identifies Dog and his crew as the culprits. Back at the bar, they send Tom out to dispose of the antique shotguns—the only remaining evidence linking them to the case. Chris then arrives to give back the duffel bag, from which he has taken all the money for himself and his son, and which is empty except for a catalogue of antique weapons. Leafing through the catalogue, the friends learn that the shotguns are actually quite valuable as they worth £250,000 to £300,000, and quickly call Tom. The film ends with Tom hanging over the side of a bridge, with his mobile phone stuffed in his mouth and ringing, as he prepares to drop the shotguns into the River Thames.