As he follows a stag during a hunt, James Fitz-James becomes lost in the Highlands. He wanders around until he comes to Loch Katrine, a beautiful lake surrounded by steep mountains. There he meets the lovely Ellen, who tells him that his coming was foretold by Allan-Bane, an ancient minstrel who serves her father. When she offers the hunter food and shelter for the night, Ellen does not volunteer her name or anything of her family history, and out of courtesy he does not ask questions. Fitz-James is disturbed, however, because the young woman bears a marked resemblance to members of the Douglas clan, a family banished by the king. When he departs the next morning, he still knows nothing about the young woman whose beauty and grace have deeply touched his heart.

Fitz-James is correct in his fear that Ellen is of the Douglas clan. Her father is James of Douglas, once a powerful friend of the king but now hunted and with a price on his head. He and Ellen and his sister are protected by Roderick Dhu, a rebel against the king and the leader of a large and powerful Highland clan. Roderick Dhu wants Ellen’s hand in marriage, but although she honors him for the aid he has given her father, she detests him for his many cruel and merciless deeds. He kills and plunders at will, trying to avenge himself on the king and the Lowlanders who, he believes, have robbed him and his people of their land and wealth. Among the men he hates is Malcolm Graeme, a young nobleman, Ellen’s former suitor, whom she loves. After Ellen’s refusal of his proposal, Roderick Dhu calls his clan together to fight Malcolm and the other supporters of the king. He claims that he fears Malcolm will lead the king to Douglas’s hiding place.

Like lightning, burning beacons and swift-riding messengers carry through the Highlands word that the clan is gathering. Young grooms leave their brides at church doors, and boys replace fathers who have died since the last gathering. The women and children are placed on a lonely and protected island for safety, for a fierce and dangerous battle is to be fought. A hermit monk prophesies that whichever side spills the first foe’s blood will be the victor. The prophecy suits Roderick Dhu, whose men have seen a spy lurking in the mountains and even now have lured the stranger into paths that will lead him into a trap. He will be killed by Roderick Dhu’s men, and thus the Highlanders will be assured of victory.

James of Douglas leaves Ellen. Although he does not tell her his destination, she knows that he is going to give himself up to the king in order to prevent the bloodshed of a great battle. After he goes, Allan-Bane tries to cheer Ellen by telling her that his harp sings of glad tidings, but she will not hear him. As she sits grieving, Fitz-James appears again. Ellen knows that he has been tricked by Roderick Dhu’s men, for no one could gain entrance to a place so hidden and secret without their knowledge. Fitz-James, refusing to heed her warning, asks her to return to the court with him. She refuses, telling him of her love for Malcolm Graeme. Fitz-James then removes from his finger a ring that was given to him by the king and explains to her that the king owes him a favor and will grant any request made by the bearer of the ring. A safe journey through the Lowlands is also promised to anyone wearing it. Fitz-James places the ring on Ellen’s finger and then departs quickly.

His guide leads him through the mountain paths until they come upon a crazed woman who sings a warning song to Fitz-James. The guide thrusts his sword into her, and Fitz-James then kills the guide. He goes to the side of the crazed woman, who, before she dies, tells him that Roderick Dhu killed her lover and caused her to lose her sanity. Fitz-James vows that he will meet Roderick Dhu and avenge the woman. Having been warned by her as well as by Ellen, he travels on cautiously. When he stumbles on a sentry stationed by a watch fire, the sentry calls him a spy, wanted by Roderick Dhu, but offers him rest and safety, for the laws of the clansmen demand courtesy even to one’s enemies. The guard promises to lead Fitz-James safely through Roderick Dhu’s lines and—even though Fitz-James calls Roderick Dhu a coward and a murderer—keeps his word. When they reach a place of safety, the sentry reveals himself as Roderick Dhu. His promise fulfilled, he then challenges Fitz-James to a duel. In personal combat Roderick Dhu proves the stronger, but Fitz-James, who is more skilled, overcomes the rebel. Then Fitz-James blows his horn and calls his men to carry Roderick Dhu to a prison cell.

In the meantime, James of Douglas has gone to the court to give himself up. First, however, he takes part in some games being staged that day and wins every event he enters. The whisper goes through the crowd that only a Douglas could possess such skill and strength. Douglas then offers himself to the king as a ransom for his friends and clansmen. When the king orders him thrown into prison, the people side with Douglas and are ready to rise against the king, but Douglas quiets them, for he will not act against his monarch. He allows himself to be taken, and the king sends messengers to the Highlanders with word that there is no need to fight; Douglas has surrendered and Roderick Dhu is a prisoner.

Ellen, accompanied by Allan-Bane, goes to the court to seek the release of her father. The ring that Fitz-James has given her guarantees her safety along the way. Before news comes that a truce has been arranged, Allan-Bane goes to Roderick Dhu’s cell and sings to him of a fierce battle that has been fought. Roderick Dhu dies with a smile, for he believes that his clansmen have fought bravely.

Ellen prepares for her audience with the king, and Fitz-James comes to her quarters to conduct her to the court. When they arrive, she notes that everyone bows before Fitz-James; not until then does she realize that Fitz-James is in reality the king. He tells her to claim the favor promised by the ring, but it seems there is nothing left for her to ask. The king has already restored her father to favor, and Roderick Dhu is dead, so she cannot plead mercy for him. She tries to stammer something about Malcolm Graeme, and the king reads her heart, calling Malcolm to her side. He forgives Malcolm for trying to aid the rebels and redeems the ring Ellen wears by joining her with her beloved.