Let the Right One In (2008)

12-year old Oskar lives with his divorced mother in a block of flats.  Oskar's shy and meek demeanour conceals a core of bitter rage.  He is bullied every day at school, and spends his evenings imagining bloody revenge: he keeps a knife under his bed and collects newspaper articles about violent crimes.

Oskar's about to have plenty of new reading material, as a series of murders sweeps the neighbourhood.  He's somewhat distracted from his usual clipping-collecting routine, though, by meeting Eli, who is a new arrival in the apartment block.  Eli is Oskar's own age, and she rapidly becomes his only real friend.  He confides in her about the bullying, and she encourages him to fight back.

Of course, Eli and the murders are connected, something that we know even if Oskar doesn't.  The story of who is committing the murders, and why, and what will happen when Oskar finds out, is essentially what the film is all about.  

Let the Right One In is intelligently and elegantly put together, and does a fine job of juxtaposing the misery that Oskar experiences at school with his growing relationship with Eli.  While there are supernatural elements at play here, the film arguably finds horror more effectively on a more mundane level: it is pretty easy to see a parallel between Oskar's story and the real world radicalisation of alienated young men.

Note that Let the Right One In is the original Swedish version of this film; there is also an English-language remake titled Let Me In, which is apparently very similar.