After watching the film the only thing we know about Brendan (masterfully portrayed by Michael Fassbender) is that he’s Irish and a sex addict.
The film starts with multiple examples of his promiscuity. He doesn’t seem to be very happy with his life. You have an impression that every day for him is like a ground dog day; he can’t stop, maybe because he doesn’t want or doesn’t know how.
Brendan’s flat in the heart of Manhattan looks modestly furnished, the only thing in it indicating presence of his soul is a vinyl record player. We also see him at work he doesn’t seem to like: his favorite places there are the coffee room, and a toilet cabin where he can ease off the burden of his addiction. He often goes out to get drunk and pull out random women with his boss, a hedonistic and disloyal family man.
One day, Brendan’s life is disrupted by his sister Sissy (played by charismatic Carey Mulligan) visiting him. She’s an emotionally exuberant singer but an impractical person at the same time. She doesn’t have a relationship (well, we see the remains of one) and a place to stay. So she clings to her brother. He doesn’t hide she’s nuisance for him, but he stays civil for a while. They don’t have much of an interaction until Brendan’s forced out of his flat after hearing his sister having sex with his boss.
Brendan and Sissy are different: she tries to connect to people emotionally, while he just has physiological needs. Brendan understands that this is a dead end for him and he tries to escape: he throws away his porn (computer, magazines, toys), but still manages to hook up with strangers. He attempts to date a work colleague but it results, as expected, a disaster. He can’t feel anything apart from self-pity. In that he’s similar to his sister: but while for Sissy it’s a consequence of not being loved, in his case it’s self-inflicted.
His addiction makes him sick: when a bouncer prevents him from entering his regular nightclub, he goes into a neighboring gay club to get off with a man and he eventually ends up in a threesome with lesbians. In that culminating scene, the close-up shots show intense suffering rather than pleasure on his face.
Finally, he comes home only to find his sister unconscious after committing a suicide. Would this change him? Would she become a bridge to his emotional awakening. We don’t know.
But in the end the director McQueen shows Brendan sitting down on the ground under a pouring rain. It is hard for the water to get through the asphalt and it is hard for love to reach Brendan’s soul. But there is always a crack in the stone, a way out. This last cathartic scene signals hope. When one is blessed with beauty and intelligence it’s a shame to succumb to weaknesses.