Place: PerthTime: 14th century
The workshop of Henry Smith the armourer
Workmen sing in the forge, on the eve of the Carnival. Alone, Smith muses on whether the coquettish Catherine Glover will consent to be his Valentine. Mab, Queen of the Gypsies enters hurriedly, seeking refuge in Smith's workshop from pursuing noblemen. When Catherine arrives unexpectedly, Mab hides in an adjoining room. Catherine, her father the glove-maker and his apprentice Ralph enter. Catherine sings of the joys of winter, and the two men retire to leave her and Smith alone. Smith gives his beloved a rose brooch in advance of St Valentine's Day. However, a stranger now enters and asks Smith to straighten the blade of his dagger. He is the Duke of Rothsay, who proceeds to flirt with Catherine, infuriating Smith, who is about to land a blow on the Duke when Mab comes from her hiding-place to protect him. Glover returns to a scene of confusion; Catherine throws away the rose, but Mab picks it up in order to return it later.
A square in Perth
Later that evening the watch, including Glover, are on their rounds. They are scared off by revellers, who gather beneath Catherine's window. Mab joins them and dances. The Duke asks her to bring Catherine, masked, to a ball at his palace that night. Although Mab initially laughs at the Duke's fickleness, she agrees, but swears vengeance. As the stage empties, Smith enters and serenades his sweetheart, unsuccessfully. As midnight strikes, Ralph enters, drunk and in despair at not being loved. As the Duke's steward asks him where Catherine Glover lives, a lady like her gets into a litter and is driven away. Coming to his senses, Ralph sends Smith after the litter; when the real Catherine deigns to reply to her lover's serenade he is gone.
Night-time festivities at the Duke's palace.
The Duke to his friends that his latest conquest will shortly arrive and a masked lady appears, but will only unmask for him. Alone together, Mab removes her domino, then flees, leaving her lover only Catherine's enamelled rose she had been wearing on her bodice. Next Smith arrives to a deserted ballroom, lamenting Catherine's infidelity. Soon it is morning, and time for the Duke's audience. While Smith hides, the Duke receives Glover, who invites him to his daughter's approaching wedding. The Duke is surprised, and Smith bursts in and accuses Catherine of betrayal. She protests, and he forgives her, but then notices that the Duke has her enamelled rose, confirmed all his suspicions.
1st tableau - a wild spot
A few hours later; Smith is seated by a tree, his head in his hands. Ralph and some artisans try to convince Smith of Catherine's innocence. Ralph agrees to meet Smith in a duel to decide her honour. Catherine now comes on the scene and Smith says he will allow himself to be killed to restore her honour to her.
2nd tableau - the main square in Perth
Mab comes to let Catherine know that the Duke intervened to prevent the duel between Smith and Ralph. However, Glover informs Mab that his daughter has lost her mind - Catherine appears and sings a distracted ballad. To shock her back to her senses, Mab decides to appear at her window and sing a reply to Smith's serenade. Catherine regains herself, swoons in the arms of Smith, and revives believing that it was all a dream, and all prepare for a joyous St Valentine's Day.