In kind of an homage to the cheapie American horror films of the 1950s, Attack the Block is a cheapie British horror film. You know, like The Blob, where something falls from the sky, wreaks havoc on a small town, and it’s up to teens to save the day.

Many American viewers are going to have some trouble understanding what the characters are saying near the beginning, due to thick South London accents, but it’s pretty easy to figure out what’s going on.

In the opening shot a bright light up in the sky wafts earthward, unnoticed by anyone because of the celebratory fireworks down below.

We’re in the bad part of town, where Sam (Jodie Whittaker), a young nurse on her way home along a dark street, is mugged. She lives in a huge complex nicknamed “the block,” what the Brits call a counsel estate (what we’d call the projects). Coincidentally, her attackers a gang of five teenage would-be street thugs also live in the block.

Right in the middle of the robbery the source of that light in the sky appears, and it ain’t a pretty sight. Stumpy and hairy, it hits the ground, goes after the teens and is killed by their self-proclaimed leader Moses (John Boyega).

So what do you do with a carcass from another world? You bring it to the local drug dealer, hoping he’ll make a handsome offer for it. What do you do when other creatures come looking for the first one, and they’re vicious and have sharp, bright green glowing teeth? You run. But then you say, Hey, this is my turf. Then you get on motor scooters and bicycles, and you grab baseball bats and small swords and even some of those fireworks, and you stand your ground.

The film presents and holds onto the frenetic energy of its youthful cast through swirling camerawork, fast editing and loud music. There’s plenty of comic relief via the stoned-out performances of Nick Frost (Shaun of the Dead), who runs Ron’s Weed Room, and Luke Treadaway (Brothers of the Head) as the pot dealer Brewis.

On the dramatic side, Sam and her attackers are forced to work together against the common enemy, and the film settles on an examination of what it takes to be a hero, or at least a leader, by taking responsibility for your actions.

A word to the squeamish: There’s more of a body count than you would expect from a sci-fi comedy, and some of the deaths are gory. But the laughs do keep coming back, and as the film moves on, it gets easier to pick up on the accent, and you eventually understand what everyone is saying.