Dallas Film Now.

Boiled down to its essence, ‘Shame’ is a film about an addict. But because Brandon, the lead character, is addicted to sex, the issue becomes confused.

Tall, dark, and handsome, Brandon (Michael Fassbender) appears to be leading an enviable lifestyle in Manhattan. He has a good-paying job, resides in a modern high-rise with lovely city views, and wears beautiful clothes. He exudes a degree of self-confidence, walking naked around his small apartment without bothering to draw the drapes.

Yet it quickly becomes apparent that Brandon is not happy. Despite having the type of good looks that inspire women to gaze at him longingly, he pays for prostitutes, surfs for porn on his home and office computers, and adjourns to the men’s room at work so he can masturbate. And there’s no indication that he’s actually enjoying his multitude of sexual encounters.

In short, Brandon is an “orgasm addict,” to borrow the title of a song by British band the Buzzcocks. He’s moving through life like a sexual shark, always in search of his next release.

Early on, Brandon listens to — and ignores — messages on his answering machine from a mysterious woman, perhaps an old girl friend. Later, the mysterious woman turns up in his shower, surprising Brandon. But that surprise compared to our surprise when the woman turns out to be Sissy (Carey Mulligan), Brandon’s younger sister.

Sissy has problems of her own, but the chemistry between her and Brandon is a bit off. They treat each other not as siblings, but as old lovers might, and it’s queasily disturbing. Sissy’s presence serves as a catalyst, forcing Brandon to deal with reawakened memories and self-destructive behavior. He’s made a long series of bad choices over many years, and it’s taken a heavy toll on his mental and emotional stability.

Fassbender and director Steve McQueen previously teamed on 2008’s ‘Hunger,’ a dark drama based on the real-life story of prisoners who went on a hunger strike to protest their treatment. ‘Shame’ is not based on true events, but it has the powerful veracity of real life, and is all the more powerful for being so realistic and harrowing in its depiction of an all-consuming addiction.

In an extraordinary performance, Fassbender bubbles forth with emotional pain. He’s struggling mightily to keep it under control, channeling his energies into sexual activity to disguise his feelings and try to dissipate his raging depression. But his thin veneer of respectability is melting under the heat of his pent-up desires; he may be having sex all the time, yet it’s all accomplished without true satisfaction.

Mulligan is rather terrific as his sister, a miserable woman who deals with her own problems with a different type of socially unacceptable behavior. She’s in just as much pain as her brother, but he refuses to provide her with what she wants.

The lingering power of ‘Shame’ is that it makes us wonder what Brandon will do with his life. It’s haunting to consider the consequences if he continues to make the wrong choice, again and again and again.

‘Shame’ opens today at Angelika Dallas and Angelika Plano.