Poised for big stardom (at least among some of us who watch a lot of fringe cable) is the exotic Romola Garal, the striking woman at the heart of BBC America’s “The Hour” who is now starring in an ambitious and artful two part adaptation of a tale of power and sex in Victorian London, “The Crimson Petal and the White” (Encore, 8 p.m.).

Based on Michel Faber’s 2002 novel, the BAFTA-nominated miniseries stars Garai as the wily and intelligent prostitute named Sugar. Her way out of a brothel run by a madame played by Gillian Anderson is through the advances of a haughty businessman, who is played by Chris O’Dowd, best known for his comic roles in “Bridesmaids” and “Friends with Kids.”

It’s a change for O’Dowd, who is utterly believable in the role. Sugar finds a way to turn tables on him by ingratiating herself into his family. Adapted by Lucinda Coxon and directed by Marc Munden, it’s a dizzying look at Victorian times that’s much more eyeopening and engrossing than the usual costume drama.

And it wasn’t an easy gig, Garai told reporters at the TV Critics Press tour last month.

“The look of the character was very important. She’s described in extreme, painful detail in the novel. She has a skin condition, which required some prosthetics every day,” Garai said. “My own hair is not red, and she is a vibrant redhead. So I was wearing a wig. And, also, the way she’s costumed is extremely important because the costumes are a source of huge symbolic importance in the novel in describing her journey. So it was always very significant, what I was wearing, and there was a lot of care and attention paid to those decisions, and I was very fortunately allowed to be involved in those decisions as well.”

To create his character, O’Dowd said, “I always felt that it was there was so much to draw from in the book that you could almost get bogged down in it. I feel like we were in one of those very fortunate positions where Lucinda had managed to squeeze the most beautiful things from the novel onto the pages of the script. So I kind of just use that as a reference.”

Coxon, for her part, said the density of the book caused some practical problems. “The first challenge was, when I was working, it was too heavy and too big to carry around with me, and so I had to confess that I’d torn it into four parts, which I have never done with a book before. It was very hard to do. I felt like a real Nazi. So I ripped it into pieces to start with.”

Once she did that, though, she found the novel “an embarrassment of riches. So, in a sense, I was in an enormously luxurious position where I just had to choose the stuff that best served our story.”

“The great success of the novel is that all of the characters are portrayed with great humanity even when they behave in a way that is manipulative,” says Garai. “They are all in an attempt throughout the novel to grab as much power as they can for themselves. And the reason that it is such a violent fight is because they are living in a society that allows none of them any personal freedom at all. And that is the great triumph of the novel, really, is that you feel sympathy for all of the characters locked in that web of desperation.”

“The Crimson Petal and the White” concludes with part two Tuesday at 8 p.m. on Encore.