The city of Rethra, near the Laba (Elbe) in the Slavonic territories on the Baltic shore, 9th or 10th century
Mstivoy’s lands. Maidens are weaving garlands for the midsummer holiday. Mstivoy’s daughter Voyslava is troubled; her passionate love for the young Arkonian prince Yaromir has led her into wrongdoing – she has killed Mlada, Yaromir’s bride. Faithful to the memory of his beloved, Yaromir has spurned her. She calls to Lada, the goddess of love, for assistance, but her crime has turned the beneficent deities against her. Her old nurse Svyatokhna promises help if Voyslava will pledge herself to Morena, goddess of the underworld. Voyslava agrees; thunder is heard, the scene is plunged into darkness, and before her stands not Svyatokhna but Morena herself, who calls upon the dark forces on Voyslava’s behalf.
Yaromir arrives with his retinue to celebrate midsummer. Morena’s spell begins to work: struck by Voyslava’s beauty, Yaromir pledges his troth to her. Mstivoy orders a dance of celebration (a redowa). Yaromir falls into a charmed sleep, and in a vision sees how Voyslava had murdered Mlada with a poisoned ring. He awakes in confusion. Servants of Mstivoy summon him to the festival.
A lakeside valley outside the Temple of Radegast. Tradespeople from many countries have gathered for the festival. A fight nearly breaks out between the Polabians and the Novgorod merchants, but the bard Lumir calms them, reminding them of their common enemy, the Teutonic Christians. The princes of the land assemble in a procession. The High Priest leads a divination rite. Mstivoy orders entertainment (Lithuanian Dance; Hindu Dance). The ritual of wreaths and idols now begins with a khorovod, in which couples kiss periodically. At each such moment, however, Mlada’s shade materializes between Voyslava and Yaromir, separating them; Yaromir rushes off after the shade. Voyslava curses Morena, whose spell has proved weaker than Yaromir’s love for her rival. Mstivoy leads his daughter away, commanding that the khorovod continue. It reaches its climax with the ritual casting of wreaths on the waters of the lake.
A gorge at the summit of Mount Triglav (Three Peaks); night, lit by shooting stars. The shades of departed souls weave their midsummer garlands (Fantastic Kolo). The moon rises, revealing Mlada leading Yaromir up the mountainside. He pleads with her to forgive him and admit him to the silent world of shades, but she disappears, telling him (by gesture) that he must endure the trial. The moon turns crimson; subterranean thunder announces the beginning of a Witches’ Sabbath. The bright shades disperse, to be replaced by Chernobog’s entourage of monsters and demons (Hellish Kolo). Morena beseeches the evil god to break Lada’s spell and let Voyslava gain Yaromir. At Chernobog’s command the sorcerer Kashchey conjures up a vision of Cleopatra to seduce Yaromir. The cock’s crow brings the orgy to a halt. Morning finds Yaromir asleep beneath a tall tree. Awakening, he decides to return to the Temple of Radegast and ask the priest to explain the meaning of his visions.
The Temple of Radegast. Yaromir makes his way to the temple and watches the priests perform their ceremonies. The High Priest bids him await dark, when the shades of ancient heroes will appear to reveal the truth. Night falls; the shades arrive and tell him ‘Voyslava has indeed poisoned Mlada; avenge her!’. Voyslava enters in pursuit; she confessed her crime but tries to excuse it by her love for Yaromir. But he seizes her by the hair and runs her through with his sword. Dying, she calls on Morena to avenge her. The goddess commands the dark forces to send storm and earthquakes to destroy the temple; the lake overflow and the city of Rethra is submerged. When the storm subsides a rainbow lights the air, and the shades of Yaromir and Mlada are seen embracing atop the Holy Rock, surrounded by all the beneficent deities.