Dawn over the Moskva River. The bells of the Kremlin, deep and massive, toll. Red Square, deserted in the early morning, is pocked with the violence of a mob uprising the night before. Russia is in turmoil. So begins Khovanshchina by Modest Mussorgsky (1839-81), unfinished at his death from alcoholic delirium at the age of 42, and one of the unsolved riddles of the operatic repertoire.