What is the synopsis of opera 'boris godunov'?

Answer 1

Presume you mean the well known opera by Modest Mussorsky and not the minor work by Johan Matheson (1681)

Russia and Poland, 1598-1605.

Exhorted by the police, the Russian people entreat Boris to accept the vacant throne. At his coronation he experiences pangs of conscience, since he had the young Tsarevich Dimitri murdered. In the Chudov Monastery, the old chronicler Pimen tells the young novice Grigory of these events, and Grigory vows to avenge the Tsarevich. He runs away from the monastery, joining the itinerant monks Varlaam and Missail and, at an inn, escapes from the police and crosses the Lithuanian frontier. The scheming Prince Shuisky, Boris' adviser, exacerbates the Tsar's guilt and he begins to hallucinate. Grigory has gone to Poland and declared himself to be the Tsarevich Dimitri. Urged on by the Jesuit Rangoni, who wishes to convert Russia to Catholicism, the princess Marina accepts Grigoriys love. The tormented Boris is told by Pimen of a miracle at the Tsarevich's tomb. This news induces a seizure in Boris who, naming his son Fyodor as his successor, dies begging God's forgiveness. In the Kromy Forest, Varlaam and Missail incite the mob in support of Grigory, who invites all to join him on the march to Moscow. The Simpleton is left alone to bewail the fate of Russia.

The original version did not include the Polish or Kromy Forest Scenes, but did include a scene before the death of Boris in St Basil's Cathedral square in which Boris is confronted by the Simpleton, who refuses to pray for him.