The action takes place in the late 14th Century at Marienburg, the present-day Malbork, in the vicinity of Gdansk.

Prologue

The Germans are laying waste the Lithuanian countryside, and from the fortifications of a castle Albano, an elderly bard, describes their advance. Aldona enters with her retinue and enquires after her brother Arnoldo, who left with her hus­band, Walter, for the battlefield that morning. Upon learning that the two men have still not returned, all offer a prayer for the salvation of Lithuania and her people.

Arnoldo, returning with Walter, announces that Vitaldo, a captain of mercenaries, has defected to the Germans and that the day is lost. All but Albano and Walter leave. Walter says that he will put into effect a plan for saving their country suggested some time earlier by Al­bano and asks Albano to wait for him by the bridge, as he wishes to bid farewell to his wife. After Albano's departure Aldona enters and Walter tells her he has to leave her. When she asks to accompany him, he tells her that his road will be one of blood and betrayal and he must travel it alone. When her brother, Arnoldo, enters, Walter entrusts his wife to him and leaves.

Act One

It is ten years later. In the public square of Marienburg in front of the Cathedral, the people are celebrating the election of a new Grand Master of the Knights of the Cross, Corrado Wallenrod. Vitoldo is among the crowd and seeks to discredit Corrado’s name.  Lithuanian prisoners to be put to death are brought in as the sound of an organ is heard from the Cathedral and the new Grand Master makes his entrance. Vitoldo calls for the prisoners’ death, but Wallenrod frees them, claiming he has received word from Heaven.  All leave, only one prisoner remains. It is Arnoldo who recognises in Corrado Wallenrod his brother-in-law, Walter.

Soon Aldona, dressed as a pilgrim, comes in and is joyfully reunited with her brother. He had left her in a convent, but she has not taken the veil; instead, she is travelling to Marienburg in search of her husband. Arnoldo tells her that Walter is alive and that he has recognised him as the Grand Master of the Knight, of the Cross. They are about go to him when Albano, who is still with Walter and who alone knows his secret identity as Corrado, bars their way. The three Lithuanians recognise one another and swear to avenge their country.

 

Act Two

In the Great Hall of' the Castle a feast is in progress. After a series of dances, Corrado calls for a bard’s song and Albano brings in Arnoldo and Aldona disguised. When Arnoldo sings a ballad of the oppression of Lithuania the assembled company demands his death. Corrado is about to fight with Arnoldo when Aldona throws herself       between them: Corrado recognises  them and has them taken prisoner for their own protection. The dances resume.

 

Act Three

Scene One

Three months later. The Lithuanians and Germans are at war and fleeing soldiers are aided by women. Aldona, coming from an oratory where she has been hiding, is afraid that Walter is dead. Albano, fearing that Walter/Corrado is weakening in his resolve to save Lithuania, arranges for him to meet with his wife, Aldona, in the hope that she will revive his flagging spirit. Husband and wife reminisce about their happy youth together in the valley of Kovno.  He leaves for Marienburg to lead the Lithuanians against the Teutonic Knights, of whom he is ostensibly the leader.

Vitoldo and a group of knights, judges of' a secret court, the Vehmgerich, enter and swear vengeance­ on Corrado:  they have learned his true identity. Aldona overhears them and resolves to save her husband.

Scene Two

In a hall in the Castle Walter/Corrado tells Albano that he has been found out by the judges of the Vehmgericht and has been condemned to death by them. The voices of Vitoldo and the Vehmgericht judges are heard approaching from outside the hall. Rather than be taken alive by them, Walter drinks poison.  The knights led by Vitoldo, burst into the room; other voices outside are heard proclaiming victory for the Lithuanian forces. The latter, with Arnoldo and Aldona at their head, burst into the room and subdue Vitoldo and the Vehmgericht.  As Walter dies, a martyr to his country voices of the Willies* are heard, pardoning him.