Some movies prosper by showing us the world that we'd prefer. Some dare failure by showing the world that is.

Such a movie is the excruciating, unpleasant and brilliant "The Mother," by two major-league bad news bearers, the director Roger Michell and the writer Hanif Kureishi. Both are men primarily known for wit: Michell directed the highly successful Hugh Grant comedy "Notting Hill," and Kureishi wrote "My Beautiful Laundrette" and "Sammy and Rosie Get Laid."

But in this film, they're playing for real. It's a look at some of the most flinch-inducing subjects of human reality, such as the sexuality of the elderly, the dreary lassitude that covers ancient family hostility, the folly of both men and women, and, encompassing all this, a universe where love has really worn down or out, if it existed to begin with.

In outline the film seems plenty appalling: Mum (in her late sixties) starts sleeping with daughter's boyfriend (mid-thirties). Complications: screaming fit, accusations, frostiness, glumness, depression and, finally, near-fatal despair, an Oedipal knot so tightly bound it would take a samurai sword to sunder. Do you require a moment toward the end where love is affirmed, where forgiveness is granted, where moral order is restored? Shop elsewhere, pilgrim.

In practice, "The Mother" is appalling, a hard, long sit. Both Michell and Kureishi focus with a clinician's intensity on the pathologies of this one spectacularly twisted kinship entity, and will not look away even in the most harrowing of circumstances. Yet in that perverse honesty, there's a kind of honor and also, particularly for people who see dozens of big studio films directed by teenagers and written by committees, the abiding pleasure of director and writer in complete synchronization, committed to the sting and bite of the actual, without homily or bromide or posture.

Begin with May. Played by the brilliant British actress Anne Reid, she's a grandma. But she's not one of those avuncular, rosy-cheeked American fantasies, a font of wisdom, kindness and gusto. One look at May's dour face and droopy body suggests a woman well used by, and well sick of, life. Her husband, Toots (Peter Vaughan), is even older, in poor health, a kind of fake-hearty who's all pink bravado and forced charisma, but has to rest and wheeze up gobs of phlegm every few minutes. May isn't in love with him anymore, she's in habit with him; he's simply a presence in her life that she presumes will never go away.

On a trip to London, the two elderlies visit their kids -- writer Paula and biz whiz Bobby -- and grandkids. It seems mostly like empty ceremony, as do so many family gatherings: The two kids pay de rigueur homage to their parents but at the same time don't really see them. There's a marvelous moment -- technically marvelous, I should clarify, but emotionally heartbreaking -- when in the morning at breakfast, everything's abuzz with hubbub, and then suddenly: silence. The two old people, who went for succor and acknowledgment, are just as alone as if they'd stayed in their far suburb. Their kids and grandkids really didn't have any interest in them.

Michell is particularly eloquent at locating the echoing loneliness of the nominally warm, crowded family bosom. A glimpse of May's stricken face as she feels the emptiness beckon her, even in the midst of cranked-high family ruckus, is as terrifying as any special-effects explosion. He cuts from that to black -- a long, empty second of nothingness on the screen, unscored, uncommented upon, a simple proclamation of spiritual emptiness -- that feels as if it weighs tons.

Enter, on cue, stage left, death. Toots passes. Nothing melodramatic: a sickness in the night, a rush to the emergency room, the clumsy awkwardness of everybody pretending a tragedy has occurred, and his still form in the hospital bed. Is there love in the grief? If you ask me, there's not much; there's just some relief.

Then May decides she can't go home. There's nothing at home. Of course this completely ew-scrays the life and times of son and daughter and, through the added pressure of mum's lengthy presence, we see that each, though having pretended to a healthy, prosperous life of success, is pathetic, incomplete and desperate. Paula (Cathryn Bradshaw), in her boho clothes and Birkenstocks, has had no success as a writer and hates herself; she lives alone in a basement flat, teaching "creative writing" to other, even less talented failures, while sleeping with a virile if somewhat unreliable contractor who will not leave his wife.

That same contractor, Darren (Daniel Craig, who looks as if he stepped out of a D.H. Lawrence novel) is working on an addition to the comfy, hip manse of Paula's brother, Bobby (boyish Steven Mackintosh), unaware that Bobby's business empire is collapsing. He hasn't the money to pay his debts and is bluffing Darren through the job so he can sell the house. In other words, nearly everyone in this movie is a hypocrite, a liar, a self-deluded self-hater, a whiner, a bitter disappointment to family and self. Just like, oh, you know, all of us.

Left alone at Bobby's house with the virile, leonine Darren, May feels things she's never felt before, and damned if Darren, a hunk and a half, isn't responsive to her primal vibrations. You can see the collision approaching, and one of the sick fascinations of the work is the inevitability of the catastrophe. Nobody is capable of saying no to anybody else, or more importantly, to themselves.

What a mess! But what ecstasy, too. May has never had sexual release of the sort that Darren ultimately delivers and soon enough she's addicted, even enslaved. You perhaps do not care to see a 65-year-old bedded lubriciously by a 35-year-old? Too bad. The movie has no pity for you. As for May, she realizes the fragility of her daughter and the cold self-regard of her son. It's not as if her eyes are wide shut; they're wide open as the family detonation approaches. She even makes it inevitable by recording her erotic posturings (extreme) with Darren in pencil drawings, which she leaves around for discovery.

The performances are brilliant. Michell and Kureishi give us a portrait of humanity that's all warts: We're little twitching bundles of flaws united by bad judgment, mendacity and hopelessness. You may not enjoy "The Mother" (I certainly didn't), but it's a movie so heavy on truth, its spell cannot be denied.

The Mother (112 minutes, at Landmark's E Street Cinema, Cinema Arts Theatre in Fairfax and Cineplex Odeon Shirlington 7) is rated R for sexuality.

May (Anne Reid) finds sexual rebirth with Darren (Daniel Craig), a man half her age.A widow (Anne Reid) beds the man who's sleeping with her daughter (Cathryn Bradshaw) in "The Mother."