Was it Something I Said? - S1.E10

Susan reluctantly does a favor for Jack by attending a charity function with Jack, his wife Margo, and her incredibly obnoxious brother. When Susan finally tells the creep off, Margo and her brother storm out, leaving Susan alone to deal with an inebriated Jack, who winds up spending the night on her sofa. But the next day Margo is not quite willing to believe that's all that happened.