Joe Cornish’s Attack the Block is a workmanlike alien invasion film, and also something more. Set in a poor London neighborhood, the movie also offers sly commentary on race and class. Wisely, it draws no conclusions, instead inviting us to decide where exactly our sympathies lie. Characters speak in infectious shorthand, and have their share of perfect one-liners.  As science fiction, the movie covers little new ground: the violence is energetic if not particularly inventive, and the aliens look like oversized, glow-in-the-dark balls of fur. This is a rare genre film that is more thoughtful than it is entertaining.

Moses (John Boyega) and his buddies are teenage criminals who steal from Sam (Jodie Whittaker), a woman who walks by the “block” (slang for an apartment complex) alone one evening. Moments later, an alien crashes on a parked car, and Moses kills it with the help of Dennis (Franz Drameh), Jerome (Leeon Jones), and the others. Moses uses the carcass to curry favor with Hi-Hatz (Jumayn Hunter), the gangster who runs the block.

Soon more aliens descend on the building, except these ones are nastier, with jet-black fur and rows of glowing teeth. Moses and Sam form an uneasy alliance – she lives on the block and works as a nurse, yet is angry about the earlier theft – as the aliens launch a full-out assault on the building. With few alternatives, everyone retreats to Rob’s (Nick Frost) weed room, but even that stronghold offers little protection.

The atypical heroes are the source of the movie’s freshness. They do not speak in platitudes, and their “us vs. them” attitude is what drives the narrative.  To Moses (who is black) the aliens are just another way to stir trouble, and he only sees Sam (who is white) as an ally once she tells him she’s his neighbor. These two are the main way Cornish uses his film as social commentary; Moses is a criminal, for example, but he also has fierce loyalty and an absent family. Sam is not let off the hook, either, for she lets the robbery confirm her prejudices. Like the other actors, Whittaker and Boyega wisely underplay the tension so it simmers. Relationships grow and readjust constantly, and once the cops arrive, the characters’ attitudes only get more complicated.

Cornish’s style is lean and efficient, and he handles the action sequences with gritty style. In one memorable sequence, the boys run from the block’s roof to the ground floor, with each one stopping at home for a weapon and perfunctory conversation with their parents. Later, two pre-pubescent boys dispatch an alien with a bottle rocket and a squirt gun. Cornish uses his setting as an opportunity for innovation; by thinking about how these characters might combat alien invaders, he finds clever ways for them to interact. The humor grows with their sense of terror, particularly as Rob and the boys goad each other toward heroism.

Unlike Europe and most American cities, Attack the Block opens in DC after the London riots. With a hood and bandana covering his face, there are times where Moses resembles the looters who kept popping up on YouTube. Later, Moses suggests the alien invasion is part of conspiracy against those like him, and the recent riots add unexpected prescience to his outrage. Such a context does not necessarily deepen sympathy for Cornish’s characters, yet it challenges us to think critically. Audiences are talking about The Help as the summer’s weightiest movie, but I have a sneaking suspicion that, in its own way, Attack the Block hits a rawer nerve. Believe it.