Hedy Carlson (Jennifer Jason Leigh) appears at the apartment of Allie Jones (Bridget Fonda) when Allie is at her neediest-she has thrown out her unfaithful boyfriend (Steven Weber) but she's still on the verge of calling him back. The surviving half of a set of twins, Hedy perpetually seeks someone to complete her, and sees in the chic and articulate Allie everything she would like to be. So Hedy moves not only into the apartment, but into the most personal aspects of Allie's life, including having her hair styled and colored to exactly match her roommate's. But when Allie reconciles with her boyfriend, their unspoken bargain-intended to help both survive in the vast and often frightening canyons of New York City-goes terrifyingly awry, driving both women to their most primal extremes from which only one can emerge.