Scene 1
Shepherds are watching flocks at dawn on the shores of Loch Katrine, and men in the nearby forests are hunting (Chorus: "Del di la messaggiera"). Elena crosses the lake and sings of her longing for her true love, Malcolm (Cavatina: "Oh mattutini albori"). At the edge of the lake, Elena meets King James who has disguised himself as "Uberto" in the hope of meeting the beautiful Elena. Elena thinks him a lost hunter and offers aid. James agrees and the two go off toward Elena's home (Duettino: "Scendi nel piccol legno"). Meanwhile the men in his entourage search for the disguised King (Chorus: Uberto! Ah! dove t'ascondi?).
Scene 2
Upon arrival at Elena's home, Uberto/King James see the insignias of his ancestors and learns that Elena's father is Douglas, the King's former tutor now turned against the King. Elena's friends arrive and sing of her betrothal by her father to Rodrigo, chief of a Scots tribe opposed to King James - the Highlanders. Uberto/James becomes jealous. He determines, however, that Elena is not in love with Rodrigo (Duet: "Le mie barbare vicende") and leaves Elena's house somewhat encouraged about his own prospects (Duet: "Cielo! in qual estasi!"). Malcolm arrives, having determined to join the Highlanders. Alone, he sings of his fond memories of Elena ("Mura felice... Elena! oh tu, che chiamo"). Unseen, Malcolm then watches Elena and her father discussing her upcoming marriage to Rodrigo. Douglas orders his daughter to marry as he has commanded, despite her reluctance (Aria: "Taci, lo voglio, e basti"). After Douglas leaves, Malcolm approaches Elena and they pledge their undying devotion to each other (Duettino: "Vivere io non potro").
Scene 3
The Highlanders' warriors welcome their leader Rodrigo (Chorus: "Qual rapido torrente"). Rodrigo is anxious to see his future bride (Cavatina: "Eccomi a voi, miei prodi"). She arrives with her father. Douglas reminds Elena of her obligation and Rodrigo declares his love. Malcolm arrives to join the Highlanders and Rodrigo introduces Elena as his bride-to-be. Despite Elena's efforts to hide her emotions, both Rodrigo and Douglas perceive a connection between Malcolm and Elena. Serano enters to warn of an attack by the King's forces. Rodrigo, Malcolm and the Highlander warriors prepare to depart for battle ("Su...amici! guerrieri!").
Scene 1
Uberto/James has come to find Elena in the hope of saving her from the coming battles (Cavatina: "Oh fiamma soave"). Meanwhile Elena asks Serano to find her father who she is expecting to see before he goes off to fight. Uberto/James approaches Elena and declares his love. She tells him that she is in love with another. Nevertheless, Uberto gives Elena a ring which he tells her was given to him by the King. He tells her it will see her through times of danger. Uberto/James prepares to depart, but Rodrigo has overheard the prior exchange with his bride. Overwhelmed with rage and jealousy, Rodrigo orders his men to kill this stranger. Elena pleads with Rodrigo's men, and then Rodrigo determines to duel with Uberto himself. The two men exit, as Elena tries in vain to calm the situation.
Scene 2
Malcolm, taking a break from battle, is looking for Elena. Serano tells him that she has gone after her father Douglas who is travelling to the King's palace seeking peace. Rodrigo has been killed and the Highlanders face certain defeat. Malcolm heads toward the palace, determined to rescue Elena from peril even if it means risking his own life (Aria: "Ah! si pera: ormai la morte!").
Scene 3
At the palace, Douglas begs his former student King James for forgiveness, but the King refuses. Meanwhile, Elena has separately gained entry to the palace by showing her ring from "Uberto". She hopes to save the lives of her father, Malcolm and even Rodrigo (unaware of his death). In the next room she hears the voice of "Uberto" who is singing of his love for her ("Aurora! ah sorgerai"). Elena is thrilled, certain that Uberto will help her gain an interview with the King.
Scene 4
The members of the King's court have joined him in his throne room (Chorus: "Impogna il Re"). As Elena attempts to approach the King, the mystery is revealed to her: Uberto and King James are one and the same. James, softening his stance due to his affection for Elena, decides to forgive both Douglas and Malcolm. Elena rejoices to have saved both her father and her true love Malcolm, while everyone else rejoices that peace has been restored (Rondo: "Tanti affetti in tal momento!")