Act 2：The ballroom of the palace of the Count Albert LaskiThat evening, a ball is being held at Laski's house, under the cover of which Laski and his co-conspirators wish to complete the details for Henri's departure. When the dancing is over, the Duke and Duchess of Fritelli arrive and introduce a new conspirator as the Count de Nangis (in reality the king in disguise). Henri (as Nangis) tells them he is no longer Henri's friend but his greatest enemy.Alone with Fritelli, Henri is astonished to discover for the first time that Alexina is married to Fritelli, but before he gets any further, Minka and other slave girls enter singing, during which the voice of the real Nangis (who should be under lock and key) is heard outside. Minka believes that Henri has become a traitor to the king but does not yet know his true identity. When she tries to leave to warn the real Nangis, Henri orders Fritelli to lock her up in an ante-room.Alexina returns and Henri, to be alone with her, hurriedly sends her husband away. Alexina is still furious that Henri left her in Venice without a farewell but during the ensuing duet he gradually wins her round and their feelings are rekindled. They are interrupted first by Fritelli, then by Laski and the Poles who have come to swear in Henri as a conspirator. Henri assures Laski that there will be no problem is getting hold of the king - he will be here soon; all Henri needs is a few moments to arrange this.Alone, Henri summons Minka and tells her that Nangis must come at once. Minka calls him - and he shortly climbs in through a window and is immediately arrested. Everyone, including Minka, is convinced he is the king and behaves accordingly; Nangis himself is mystified until - in asides - Henri commands him to play the part, which he does with relish. Henri tells Nangis that they are resolved that the king leave Poland forthwith. Laski then orders Nangis and Minka to leave. To the horror of the conspirators he tells them that the only way to ensure that the king does not return is to kill him that very night. They draw lots and Henri is chosen to do the deed, but at that moment Minka re-enters, and boldly announces that she has set Nangis (they think: the King) free, and the act closes with the fury of the Polish nobles, and Henri swearing again that he will get rid of the king.