Unceremoniously dumped by his college girlfriend Margaret during a trip to Cambodia, lovelorn American Keith returns to Philadelphia and teams with his best friend Chainsaw to form a "relationship investigation" team devoted to revealing unfaithful husbands, wives, boyfriends, and girlfriends for the two-timing louses that they truly are.

When Billie learns that her estranged parents' lives are at risk, she tries to help them by robbing a bank. In her botched robbery attempt, she takes a hostage named Franny, who turns out to be a charmingly impulsive pregnant teenager with nothing left to lose. Together, Billie and Franny embark on a chase through scenic American landscapes, clashing and struggling for common ground in hopes for a brighter future.