The action takes place between February 20, 1598 and April 13, 1605.
The police urge the people to petition Boris to assume the throne, but the common people have too many troubles of their own to be interested in a public demonstration. Finally, however, they bow to the browbeating of the authorities.
Boris has agreed to accept the pleas of the people and is to be crowned Tsar. The coronation moves past the Kremlin and into the Cathedral.
In his cell in the monastery of Chudova, Pimen the chronicler is writing a history of Russia. He concludes it with the murder of Dmitri the Tsarevitch. Grigory, a young novice, questions Pimen about Boris' crime and sees himself as an envoy from the higher powers, sent to expose and condemn the usurper.
Grigory has fled the monastery and arrives with two wandering friars at a tavern on the Lithuanian border. The hostess of the tavern suspects Grigory of foul intentions but helps him across the border. The police arrive with a description of Grigory and begin to ask questions, but Grigory manages to escape.
Boris' daughter Xenia mourns her dead fiancé. Her brother Feodor and the Nurse try to console the girl and cheer her up, but in vain. Boris predicts to his son Feodor, who is examining a map of Russia, that Russia will some day rule the world.
Vasili Shuisky relates the news that a pretender has arisen in Poland and attracted a great following. Boris suspects Shuisky of treachery and asks whether the boy killed in Uglitchy was indeed Dmitri the Tsarevitch. Shuisky's description of the execution of Boris' orders is so realistic that Boris is beset by visions, and imagines he sees the murdered child.
Marina Mnishek, daughter of the Voyevod of Sandomir, plans to exploit the passion that Grigory has for her: if Grigory attains power, she plans to share it as Tsarina. Rangoni, a clandestine Jesuit, makes Marina swear to use every possible means to win Grigory over.
A great feast is being celebrated in the park outside the castle in Sandomir. Rangoni tries to convince Grigory of Marina's love, but Grigory is suspicious and senses a plot against him. Once Marina arrives, however, she completely beguiles him. A passionate love scene follows, observed from a distance by the please Rangoni.
Impoverished people have gathered in front of the Cathedral of St. Basil. The pretender, the monk Grigory, is formally excommunicated, but this does not impress the people. Boris arrives in the square: the fool calls him a sinner and accuses him of murder.
The Duma has assembled in the Kremlin to discuss the uprising. Shuisky relates that the Tsar is troubled by pangs of conscience and by hallucinations, for the crime committed in Uglitchy will not allow him to rest. As Shuisky speaks, Boris enters, clearly of unsound mind. Pimen explains how a blind shepherd regained his vision upon praying at the grave of the murdered Dmitri. The boyars regard this as incontrovertible evidence of the treachery f the pretender. Boris tells his son Feodor that he wild die soon, and advises him how to rule the country whose throne he will soon assume Boris prays for forgiveness, blesses his son and dies.
The people are in revolt. The pretender and his troops arrive in the vicinity of Kromy to continue their progress towards Moscow. The common people take their anger out on one of Boris' officers. Varlaam and Misail urge the people to hail Dmitri as their new Tsar. A fight breaks out between two Jesuits and the people. Grigory arrives, and the people hail him as their savior. They follow him to the Kremlin.
The fool is left alone. He sees the future unfolding before his eyes: the eternal cycle of history continues unchanged and many pretenders will yet perish with it.