Dawn at Loch Katrine: Elena, the Lady of the Lake, makes her daily crossing while shepherds watch their flocks and men hunt in the woods. She sings of her love for Malcolm Groeme, but comes across King James disguised as “Uberto,” who hoped to meet the legendary beauty Elena. Believing the King to be a lost hunter, she offers him hospitality and they depart for her home while the King’s men search for their disguised leader.

King James learns that Elena’s father is Douglas d’Angus, his former tutor who has since joined the Highland Clan opposed to James’s rule. He also learns of Elena’s betrothal to Rodrigo di Dhu, chief of the Highland Clan, but his jealousy is assuaged upon seeing Elena’s lukewarm reaction to the prospect of her marriage. Malcolm, the suitor whom Elena loves, arrives shortly after James departs. Still, he must endure overhearing Douglas order his daughter to marry Rodrigo, as he commands. Douglas exits, leaving Malcolm and Elena to pledge their everlasting love.

The Highland warriors gather to welcome their leader Rodrigo, who introduces Elena as his future bride once she and Douglas arrive. Malcolm has since resolved to join the Clan, but his secret bond with Elena is perceived by Douglas and Rodrigo when they meet. They are interrupted, however, by news of attack by the king’s army. Rodrigo and his warriors depart for battle.

Still disguised as Uberto, James searches desperately for Elena, hoping to protect her from the coming bloodshed. He finds her and once again pledges his love for her, but she rejects his advances. Nonetheless, he leaves her with a ring that he claims was given to him by the king and will secure her protection from the king’s forces. Rodrigo overhears this exchange and attempts to have his soldiers kill the stranger, but Elena intercedes and Rodrigo vows to duel with Uberto himself.

Meanwhile, Malcolm has left the battle in the hopes of finding Elena, but is informed she has followed her father to the palace to seek peace. The Highlanders face certain defeat after the death of Rodrigo, and Malcolm pledges that he will save Elena or face his own death.

Douglas pleads unsuccessfully with his former student for forgiveness, but receives none. Elena enters the castle determined to save the lives of her father, Malcolm, and Rodrigo; she gains admittance to the king’s chamber through use of her ring.

Elena is surprised to see nobles surrounding Uberto, but it soon becomes clear that he and James are one and the same person. His feelings for her soften his attitude towards her father, and he pardons both Douglas and Malcolm. The lovers are finally allowed to be together, and all rejoice as peace reigns.