Brandon (Michael Fassbender) is a successful, handsome thirty-something living and working in New York. Unknown to those who know him, he's struggling with a sexual addiction. On a subway train he flirts with a woman and she flirts back with him. She has a wedding and engagement ring on, and when they exit the train, she disappears into the crowd. Brandon and his boss David (James Badge Dale) go out and meet women at a club. Later Brandon has sex with the woman David was trying to pursue.
In New York City, Brandon's carefully cultivated private life -- which allows him to indulge his sexual addiction -- is disrupted when his sister Cissy arrives unannounced for an indefinite stay.