IT IS obvious from the first few minutes of David Cronenberg's stylish and deeply creepy "Spider" that something is profoundly wrong with the hero, Dennis Cleg, a package of damaged human goods if ever there was one (even as played by a bit-too-pretty Ralph Fiennes). Muttering incoherently, alternately stumbling and shuffling as he checks into a rundown halfway house in a dingy London neighborhood, the title character -- so nicknamed because, I don't know, maybe he eats bugs or hangs upside down from the ceiling -- is probably, at the barest minimum, paranoid, flinching and squirming if anyone so much as looks at him funny.

As it soon becomes clear, we don't know the half of it.

In "Spider," what we are presented with is a classic example of the unreliable narrator. Except that, as Spider, Fiennes is given maybe six lines of intelligible dialogue in the entire script, adapted by Patrick McGrath from his novel of the same name. Spider doesn't so much narrate the film as he screens it for us, presenting us with a subjective reenactment of his childhood as he wanders through the neighborhood he grew up in, watching his own flickering memories unspool through the cracked projector of a broken mind.

And so we visit Spider as a boy (Bradley Hall), living with his plumber father and housewife mother (Gabriel Byrne and Miranda Richardson). We watch them eat, bicker and go down to the pub, where we see (or seem to see) his father cheat on his mother with a garish, snaggletoothed floozy. When Dad's infidelity is discovered by Spider -- and Spider's mother -- major unpleasantness ensues.

What small child wouldn't be traumatized?

Cronenberg films all this with a beautifully begrimed lens, not like a movie, but as if we were inside Spider's cobwebbed head, looking out. The world of the protagonist's childhood unfolds less like traditional flashbacks than vivid hallucinations. Even the contemporary scenes play like delusional visions. What year is this? Where are we? Nothing is ever completely clear, in a London that seems largely unpopulated, save for the sometimes shape-shifting staff and inhabitants of the boarding house from which Spider launches his peregrinations into the past, retreating to his depressing bedroom only to cower beneath a network of twine strung from wall to wall.

Although "Spider" will probably remind some viewers of "The Butcher Boy," Neil Jordan's brilliant if problematic 1997 tale of another lunatic child's descent into madness, it is emphatically Cronenberg's film. Steeped in eerie atmosphere and a sort of flairless visual flair, it parcels out the chunks of its story in piecemeal fashion, as if we were psychiatrists listening to Spider's therapy sessions, but without the ability to heal him.

In the end, when the final twist is delivered, it comes as less of a shock than a sickening fulfillment of what we should have expected. Spider, we now realize, is one sick pup, beyond all hope and happiness. His story is sad, compelling and morbidly, tragically watchable.

SPIDER (R, 98 minutes) -- Contains partial nudity, a sexual encounter and violence. At the Cineplex Odeon Dupont Circle 5 and the Cinema Arts Theatre.

John Neville and Ralph Fiennes try to keep it together in "Spider."