Businessman Henry Bell (Sam Neill) and society woman Karen Knightly (Helena Bonham Carter) meet on London's Tower Bridge, where they are both contemplating suicide. After talking, they decide to go for coffee, and together they plot to take murderous revenge on each other's nemeses -- Bruce Tick (Steve Coogan), who took Bell's job, and Imogen Staxton-Billing (Kristin Scott Thomas), who married Knightly's ex-lover. Things become complicated, however, when Bell begins to fall for Imogen.