Remember An Affair to Remember, where Cary Grant and Deborah Kerr meet, fall in love, and leave the rest to fate? Wasn’t it grand? Serendipity shares the same plot, but that’s about all. Marc Klein’s hackneyed screenplay bounces Sara (Beckinsale) and Jon (Cusack) through so many ”astonishing” parallels (both of their relationships fail at the same time — weird!) and ”cosmic” concordances (they fly to opposite coasts simultaneously — kooky!) that fate isn’t just knocking on their door; it’s broken in and is smacking them upside the head.