The sorceress Rosa Veneda discusses in her earthen grotto with her sister Lilla the battle between the tribes of the Wends and Lehits. Ecstatic visions reveal to Rosa that her witchcraft does not help the Wends to win the battle, that their homeland will be ravaged and that Lilla will die too. Lilla cries, which causes Rosa's anger: how can you cry for yourself when the knights die. Twelve old men with golden harps come in. They say that the father and brothers Lilla and Rosa - the king of the Wends Dervid and his sons Lelum and Polelum - were captured, and that the golden harp of the leader of the Wends is also in the hands of the enemies. Rose decides to curse the captives. Then Lilla goes to rescue the father and brothers. Rosa, referring to the old bards, portends that in three days there will again be a terrible battle. Only the harps of the elders - and above all the harp of King Dervid - will inflame the hearts of the knights, and then the Wends will win the battle. The sorceress calls spirits and leaves to burn the bodies of dead soldiers.
The leader of the victorious army Lech orders the captives to be brought. Dervid - with a golden harp, his two sons are chained together in one chain. Lech scoffs at them, even the high growth of Wends for the undersized Lech is the reason for ridicule. The wife of Lech Gwynon notices that the harp must be magical. The prisoners are silent. The royal couple of winners decides to starve them until they speak.
At this time, St. Gwalbert argues, being with his servant Slyaz inside the giant skull that serves as their home, that he came to proclaim the Gospel, and then the conqueror burst in and destroyed everyone before they converted. Lilla enters, she asks for the help of a saint. He explains to her that she must take a vow of chastity and seek help from the Virgin. After this, Lilla and St. Gwalbert go to Lech. Left alone, Slyaz decides to look for a more well-fed and cheerful life than a saint. He sets fire to the home and leaves.
At this time, Gwynon and Lech discuss what to do with the prisoners. Gwynon asks to give them to her, and sends her husband to hunt. Enter Dervid - he does not part with the harp. Gwynon is trying to get him to play the harp - she does not succeed. In a fury, she orders the old king to gouge out his eyes. He is taken away, after which Saint Gwalbert and Lilla appear. They ask for captives. Gwinona indifferently replies that her daughter was late. Blinded Dervid is introduced. In desperation, Lilla defies Gwynon, promising to save her father from death three times. Gwynon tells the old man to hang by the hair so that his legs almost touch the ground.
A tear falls on the battlefield, where Rosa Veneda burns the corpses of the dead. Rosa predicts to the roguish and cynical servant his role in the tragedy. After parting with the sorceress, Slyaz stumbles upon a dying knight - this is the beloved knight of Lech Salmon. A slyaz finishes him, puts on his armor and goes to Lech. Lilla Weneda is trying to save her father. Despair tells her a terrible thought: let her brother throw the ax so that she cuts off the hair on her father’s head. Lech and Gwynon agree. Bring a chain of Lelum and Poletum. Lilla begs her brother to throw an ax. Reluctantly, Polelum throws an ax - and father is saved the first time.
The appeared Slaz claims that he is Salmon, but that he was bewitched by a witch on the battlefield. Knights believe him. Only Gwynon is convinced that this is some kind of trickster. She again orders to bring Dervid - she wants to make him play the harp. Again in a rage she invents a new execution for him: she orders him to be thrown into a tower with snakes. Lech and the knights begin to suspect that Salmon is not Salmon in fact and decide to test him. A slyaz stands at the gate post, he is scared that his deception will be revealed, he does not know what to do, and then Saint Gwalbert appears at the gate. The trick changes clothes with him, leaves him at the post, and he runs. The knights grab the saint and want to kill him for allegedly pretending to be Salmon. They carry him into a tower with snakes - and they forget about him, amazed at the opened picture: Lilla Veneda plays the harp, snakes are located around her and listen, enchanted, the emaciated old man sleeps in deep sleep. "What to do?" - the knights ask Lech. He orders to lead the old man and starve him to death.
Two days later, Lilla Veneda comes to the castle in one simple shirt and in a wreath of water lilies on her head. She begs Gwynon to let her go to her father. Lech asks his wife to give in to the girl’s requests and, when she is let in, says that their son was captured by the Wends. The despair of the parents, the cries of Gwynona, Lech collects soldiers to beat off his son.
Escaped from the Lechits, Slyaz sets off to look for a better share among the Wends. He is considering options for false information, including the death of the king. With tales, he intends to earn his living.
And the triumphant Lilla enters the hall where Lech and Gwynona are killed for their son. She saved her father from starvation by feeding him the edible stems of water lilies - a custom known to the people of her tribe. Veneda asks to let them go with his father. But the insidious Gwynon tells Dervid to choose whether he will take the harp with him or take his daughter away. Lilla persuades her father, Gwynon, Lech - and finally takes her father away, promising that she will return for the harp with Lehon, a prisoner of the Wends.
The witch Rosa Veneda predicts that in a new battle, Dervid's harp will bring victory. At this time, they bring the Slash, which reports false news about the death of Dervid. Rosa immediately kills Lehony. After that come Dervid with Lilla. “Where's the harp?” - the witch asks the sister. She replies that she is in mortgage for her son. Upon learning of his death, Lilla goes to death to Gwynon. She takes the tear with her so that he brings the harp.
When Lilla appears on the threshold alone, Gwynon, realizing that her son is dead, strangles Veneda. A slaz carries a wounded harp in a case. But when, surrounded on all sides by lehits, the Wends open the case, they find the body of the dead Lilla there. Dervid dies of despair. Dies in the battle of Gwynon. Lelum and Polelum die. On the bonfire of their funeral pyre, Rosa Veneda rakes the ashes, finds the chain with which they were bound, and throws it at Lech’s feet with the words: “Look what remains of your slaves.”
