Set in a rural gray sleepy hollow that looks like the loneliest corner in all of England, ''The War Zone,'' which marks the directorial debut of actor Tim Roth, assaults you with its quietude, its frozen, portentous atmosphere of secrets festering in the dark.
In this drama of repression and incest, Tom (Freddie Cunliffe), a pimply, pale teenager, discovers that his sister, Jessie (Lara Belmont), has been sleeping with their father (Ray Winstone). Confronted with a domestic atrocity, the boy stares and stares, then stares some more. He's ''studying'' his family, especially his dad, who proves to be even more of a monster than we imagined.
The monumentally somber style of ''The War Zone,'' descended from Ingmar Bergman's famous gloom, says that there's something more horrifying going on than mere words could ever express. I generally have little patience for this brand of art-conscious dragginess, but Roth, there's no denying, creates considerable suspense out of our desire to confront the forbidden.
Tom first sees Jessie and their father in the bathroom, then hauls a camcorder up to the fortresslike bunker where the two hold their covert meetings. He videotapes one of their encounters through a slit rectangle window, and Roth, acknowledging the voyeurism implicit in our intrigue, does full, disquieting justice to the violation being depicted. Still, I wish there were more to ''The War Zone'' than the grimly unwavering power of its gaze.