With a virtually unknown cast and a minuscule budget, director Danny Boyle strips the modern horror film down to its purest form, without the spectacle and winking irony that have characterized the genre in the post-Scream era. What's left is a bare-bones story of viral apocalypse in which the zombies are merely the extreme manifestations of our own human tendencies, and the real monsters are all too human.

Though it may be easy to draw a direct line from 28 Days Later to previous works as diverse as George Romero's Living Dead films, the Charlton Heston classic Omega Man and British author John Wyndham's Day of the Triffids and Village of the Damned, the film still manages to express original ideas in way that feels fresh and raw. Certainly that sense may have as much to do with the fact that the film was shot entirely on digital video as it does with the actual narrative.

Though it often makes sense from a budgetary standpoint, DV is not ideal for every project. In this case, however, the material is particularly well suited to the grainy, immediate quality of the images it produces. The washed-out colors, from sickly yellow skies to bluish-gray urban landscapes, help to create an overall unsettling feeling. Sound plays an important role as well, or, more often, the lack of sound. The early shots that follow Jim around the quiet, empty streets of London from Tower Bridge to Piccadilly, accompanied only by a grungy guitar soundtrack, are particularly impressive, if a bit slow-moving.

28 Days Later doesn't look or feel like anything you're likely to see at the multiplex this summer. This is a film that makes you think, even in its most terrifying moments, and leaves audiences with much to ponder long after the ride is over.