The King of Lombardy has a daughter, Leonora, who has secretly married Lorenzo, the King's General. As the King is extremely possessive of his daughter, he is furious when he discovers that she has married below her social station. Lorenzo is imprisoned, but he is popular among the citizens and they start to arm themselves, calling for his freedom.
The King orders that Lorenzo's heart be ripped out and sent to Leonora (the 'cruel gift'). Antenor (the King's Prime Minister) orders his son Learchus to carry out the deed. Leonora takes the initial news of Lorenzo's death calmly, but breaks down when Learchus presents her with the cup supposedly containing his heart. She curses her father, and tries to kill herself.
The King is shocked to learn that Lorenzo was in fact the son of the Duke of Milan, and therefore suitable husband-material for Leonora. He pleads with Leonora to carry on living, but she vows to kill herself. The King bitterly repents his actions.
Near the end of the play, a very much alive Lorenzo is reunited with Leonora. It turns out that Learchus had arranged for a substitute heart to be sent to her, hoping that her grief would soften her father's heart. Learchus is rewarded by being allowed to marry his own love, Antimora. The play closes with news that the rioting citizens laid down their arms after hearing that Lorenzo was in fact alive, but that the villainous Antenor was killed in the fighting.