The libretto, by Béni Egressy, is based on the play Két László by Lőrinc Tóth.
Hunyadi László is considered to be the first important Hungarian opera and Erkel's musical style draws on folk influences, particularly the dance known as the verbunkos.
The opera was reworked in 1935 by Kálmán Nádasdy, Gusztáv Oláh and Miklós Radnai, which is what is usually performed today.
This rework changed the libretto almost completely, switched around and even removed some parts, shortening the piece by about 15-20 minutes.
The great military leader, János Hunyadi, who defended Hungary against the attacks of the Ottoman Turks is dead and power has passed to his enemies.
László Hunyadi's soldiers oppose letting the foreign king and his mercenaries into the castle since they do not trust him.
Erzsébet, not convinced about the king genuinely excusing László and still worrying for his life, has a vision about him being executed and she faints.
The king, referring to János Hunyadi's heroic deeds, promises to pardon László.
Miklós Gara, Mária's father, comes up with a plan upon seeing this: he will give his daughter's hand to the king instead of László Hunyadi, reassuring his position of power.
The king publicly vows not to avenge Cilley's death and accepts László and Mátyás as his brothers and Erzsébet as his mother.
In one revision of the opera, Gara's recitative is placed at the end of this scene and has different text more about his plans to take the throne and his success in convincing the king.
She bribed the guards and tries to convince László to flee with her, but he trusts in the king's vow and stays.