Opening late at night with an ill-fated mother and daughter having a car accident as they drive home on a lonely Romanian road, 'Them (Ils)' doesn't waste much time before delivering the first in a series of short, sharp shocks that prefigure what's to come in the rest of this bleak French thriller. Although this is the first feature from co-directors David Moreau and Xavier Palud, there's none of the clumsiness that's often associated with a debut. Instead, 'Them (Ils)' is a taut and atmospheric horror that spends most of its short running time fuelled on pure adrenaline.

After the first series of frights, there's a slight breather while the film introduces Clementine (Bonamy) and Lucas (Cohen), a French couple living in a rambling old house in a wood outside Bucharest. She teaches French in a local high school, while he works on his novel at home. All unknowing, Clementine drives past the unfortunate mother and daughter's car on her way home from work for the weekend. After a few minutes of scene setting - sympathetic characters, happy couple, domestic bliss etc - the terror resumes with some strange night disturbances. Clementine and Lucas wake at 3am to strange lights and noises. The dog disappears; their car gets driven away; there's the disturbing sound of windows shattering. The intruders, whoever - or whatever - they are have invaded their home.

The rest of the film is a succession of frightening episodes in real time. No incidental music means that we, along with Clementine and Lucas, strain to hear any sound that indicates what is happening. Ratcheting up the tension, Moreau and Palud skilfully emphasise the spooky and the suggestive, never revealing the source of the night's horrors until the very end. The two actors, Olivia Bonamy and Michaël Cohen, play the whole film straight, developing enough empathy so that the audience is with them every painful, frightening step of the way.

If you like films that set your nerves a-jangling, 'Them (Ils)' will be an edge of the seat treat; best avoided by people of a nervous disposition.

Caroline Hennessy