IT'S AWKWARD, being a sex addict. There's the possibility that your boss might discover all the porn you've got on your hard drive, or your sister might walk in on you while you're masturbating, or someone might casually open your laptop only to be propositioned by a topless girl on a webcam. In Shame, sex junkie Brandon (Michael Fassbender) runs into all of these difficulties, in between meaningless trysts with women he meets at bars and women he pays for.

Brandon is the type of guy who can pick up a woman from across a bar via intense eye contact alone, but put him at a dinner table across from a woman he actually likes and he totally falls apart. His lonely, sex-focused existence is disrupted when his sister arrives for an uninvited visit: Sissy (Carey Mulligan) is a rootless lounge singer with a host of issues of her own. Where Brandon has completely severed the connection between sex and emotional intimacy, Sissy is painfully needy, falling too hard for men she's only just met. Shame never explains what, exactly, happened to these siblings to leave them so damaged, and it doesn't really need to; it's clear from the way they interact with other people and each another that something, somewhere, went painfully awry.

Shame earns its NC-17 rating mostly through shots of Michael Fassbender's penis; its lengthiest sex scene—between Brandon and two women—comes at the end of a night of tawdry episodes that also includes fingering a chick at a bar and following a strange man into a club for a blowjob. There's not much pleasure in watching Brandon hit rock bottom, but it's to the credit of both Fassbender and director Steve McQueen that Brandon is a complex and almost wholly sympathetic character even when behaving reprehensibly. There are consequences to the pursuit of pleasure at the expense of intimacy, Shame reminds us—and watching Brandon learn that lesson for himself is surprisingly engrossing.