It's a 48-year-old argument that's once again got nuclear-armed neighbours in a showdown and locals on both sides of the border fearing the worst. India blames Pakistan for Kashmir's worst terror attack in years: the killing of 26 tourists, with non-Muslims singled out and murdered in front of loved ones. Islamabad denies involvement. It blames New Delhi for the March terror attack on a train in Baluchistan. There, too, 26 people were killed, with the matching tolls fuelling speculation and conspiracy theories. So what did happen?