In 1929, an explosion in a Missouri dance hall killed forty-two people. Who was to blame? Mobsters from St Louis? Embittered gypsies? The preacher who cursed the waltzing couples for their sins? Or could it just have been a colossal accident? Alma Dunahew, whose scandalous younger sister was among the dead, believes the answer lies in a dangerous love affair, but no one will listen to a maid from the wrong side of the tracks. It is only decades later that her grandson hears her version of events - and must decide if it is the right one.