Cardboard Gangsters follows the story of a group of young lads in Darndale, led by Jay Connolly (John Connors), who sell drugs to make a living. They set out in a bid to gain more money and power and enter the big leagues of the drug trade. Things begin to unravel quickly as not everyone in Darndale is willing to let these Cardboard Gangsters achieve the notoriety they crave without a fight.

Six friends, who've known each other from childhood, break into the tower block they lived in as kids, now deserted and condemned, to rig-up a pirate radio station, get high and party. When one of the group goes missing, her friends begin to search the dark interior of the tower and soon realize that they are not alone: a resident psychopath lurks in the shadows and is hunting them down, taking them out, one-by-one.