To map the moral boundaries of the Victorian London in which The Crimson Petal and the White is set, listen to the conversation between the teenage prostitute Sugar and her mother, who is also her pimp, and is speaking in both capacities.

“Do you remember the game we used to play when you were a baby?” asks mom, who goes by the suggestive name Mrs. Castaway. “On the coldest winter night, I’d creep into your room while you were sleeping, all cuddled up in your blanket, and I’d pull it off. ... And I’d say, ‘That’s what God does.’ ”

The Crimson Petal and the White, a four-hour miniseries airing on the Encore channel on Monday and Tuesday, is a disturbing chronicle of a young woman’s desperate attempt to negotiate a world that is cruel, irrational and joyless, torn by violence and tinged with madness.

Romola Garai, a British television actress best known on this side of the Atlantic for her role as an American teenager merenguing her way through the Cuban revolution in Dirty Dancing: Havana Nights, has a far more substantial role as Sugar, the prostitute whose sexual aptitude is matched by her simmering rage.

Sugar’s intelligence — she taught herself to read and loves Shakespeare — has only fed her determination to escape a squalid brothel so violent that most of the women have taken to carrying knives. Sugar’s weapon of choice is literary: She’s writing a memoir, “a book of hate to wreak revenge on every pompous, trembling worm who taps at Mrs. Castaway’s door.”

But the newest of those pompous, trembling worms may offer her a way out. William Rackham (played by Chris O’Dowd, whose film credits include Bridesmaids and Pirate Radio) is the hapless heir to a perfume company, a man with no interest in the business career his father has chosen for him and no talent for the literary path he prefers. His home, where his mentally disturbed wife has confined herself to one bedroom and an unloved daughter has been banished to another, is an even bigger mess.

Enchanted by Sugar’s post-coital literary chatter (they agree that Alfred Tennyson’s poetry — a line of which provides the title for The Crimson Petal and the White — is overrated whimsy) and enslaved by the acts that precede it, Rackham grows increasingly fixated on her. First he purchases the exclusive right to her services, then moves her to a tidy house away from the slums. Feeding on her ambition, he discovers an untapped gift for business.

Though her revulsion for men is only slightly diminished (she still fantasizes about disemboweling Rackham as he sleeps), Sugar latches onto his life. But his casual remark as they gossip about someone else’s romances — “What enthralls us today may simply have no hold tomorrow” — reminds her how tenuous her status is. Hoping to displace Rackham’s unhinged wife, Sugar begins stalking the woman on her dotty misadventures around town, setting an emotional collision course.

The Crimson Petal and the White is set in a labyrinth of class warfare and sexual repression. Rackham and his friends prattle on about socialism one minute, complain that “the rain makes the servants skittish” the next. By night they rampage through the city’s whorehouses, by day they refer to prostitution as “a fate worse than death.” Their moral disdain for sex and their ravenous appetite for it are locked in a deadly conflict, sometimes literally.

The male characters, beastly as they behave, are not treated entirely unsympathetically; they often seem trapped and bewildered by rules and roles that they inherited. But The Crimson Petal and the White’s real tenderness is for its wounded women, battering against gender barriers that are anything but glass. The physical violence suffered by the prostitutes is no less damaging than the psychological and emotional violence inflicted on the women on the wealthier side of London. The sadness with which Rackham’s little daughter expresses doubt about her ambition to be an explorer — “there mightn’t be permitted a lady explorer” — cuts like a knife.

Based on Michael Faber’s 2002 novel, The Crimson Petal and the White is a BBC production that aired in Great Britain last year, and though most of its cast members are little known here, they’re uniformly excellent. O’Dowd and Garai are fascinating as they make their characters grow in opposite directions — he more steely, she more compassionate — over the course of the show.

But the most startling performance may be that of the American ringer, The X Files’ Gillian Anderson, nearly unrecognizable as the flinty madame. A burned-out husk stripped of every human aspect except the survival instinct, her Mrs. Castaway is a reminder that when characters in The Crimson Petal and the White say of the dead that they’ve gone to a better place, they aren’t speaking figuratively.