Kate Dickie, Tony Curran, Martin Compston, Natalie Press Running time: 114 mins . . . .

IT'S bad enough having Big Brother snooping on you every time you set foot outside the door. But the reality is even worse. The actual staff operating monitoring cameras are free . . . should they be perversely inclined . . . to pick out anyone that might catch their attention and stalk him or her at will for whatever purpose they choose. This is the intriguing premise of Red Road, a terrific debut by Andrea Arnold, who won an Oscar for her short Wasp last year (famously declaring "this was the dog's bollocks").

Red Road was originally conceived as part of a Lars Von Trier Dogme project by which three first-time directors were chosen to take the same group of given characters and each make a different story with them set in Scotland using the same actors. Mikkel Norgaard's comedy romance and Morag McKinnon's black comedy have yet to happen, but Arnold's Red Road won this year's Cannes Camera d'Or for best first movie.

Kate Dickie plays Jackie, a uniformed guard in Glasgow who watches a bank of CCTV cameras that cover a notorious estate of rundown concrete highrise flats (soon to be demolished in real life) and alerts the police if she spots anything suspicious or potentially threatening. We get hints about her life . . . that she lives alone but once had a husband, that there's some trauma in her past, that she has occasional sex with a colleague in the front of a security van . . . but have no idea why she is so obsessed with a man she spots picking up a girl and having sex with her behind a graffiti-covered wall. Is it voyeurism that prompts her to pick him out each day and track him to his various haunts . . . and the block of flats where he lives . . . or does she know him from the past and have some dark ulterior reason for what she is doing?

Apparently he has just got out of prison, but for what crime? Why does he spend so much time with two homeless waifs? Her need to find out . . . in which we have been made worryingly complicit . . . turns her into a stalker after hours, to the point where she insinuates herself into his presence, much like James Stewart in Rear Window. Red Road, as with Michael Haneke's Hidden or Michelangelo Antonioni's Blowup, compels us to scrutinise the screen for any giveaway visual detail that may or may not be there.

Dickie is a revelation. She has an ability to be at once coldly impassive and dangerously vulnerable, particularly in a daringly erotic sex scene which turns out to be much more than it seems. Tony Curran is intriguingly ambivalent so that we're unsure whether he's a dangerous sex offender or someone she's just fantasising about. Red Road is cinema in its purest form, compulsively watchable.